U.S. patent application number 13/383205 was filed with the patent office on 2012-05-10 for atomic memory device.
This patent application is currently assigned to RAMBUS Inc.. Invention is credited to Lawrence Lai, Liang Peng, Bohuslav Rychlik, Thomas Sheffler.
Application Number | 20120117317 13/383205 |
Document ID | / |
Family ID | 43607273 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120117317 |
Kind Code |
A1 |
Sheffler; Thomas ; et
al. |
May 10, 2012 |
ATOMIC MEMORY DEVICE
Abstract
In an integrated-circuit memory device having a memory core, a
first data value is retrieved from an address-specified location
within the memory core in response to a memory access command. The
first data value is output from the memory device in response to
the memory access command, and a second data value is stored in the
address-specified location within the memory core in response to
the memory access command.
Inventors: |
Sheffler; Thomas; (San
Francisco, CA) ; Lai; Lawrence; (San Jose, CA)
; Peng; Liang; (San Jose, CA) ; Rychlik;
Bohuslav; (San Diego, CA) |
Assignee: |
RAMBUS Inc.
Los Altos
CA
|
Family ID: |
43607273 |
Appl. No.: |
13/383205 |
Filed: |
June 17, 2010 |
PCT Filed: |
June 17, 2010 |
PCT NO: |
PCT/US10/39095 |
371 Date: |
January 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61235564 |
Aug 20, 2009 |
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Current U.S.
Class: |
711/103 ;
711/105; 711/154; 711/E12.008 |
Current CPC
Class: |
G06F 2212/2024 20130101;
G11C 2207/107 20130101; H05K 999/99 20130101; G11C 7/22 20130101;
G06F 12/023 20130101; G11C 7/1039 20130101; G11C 7/1006 20130101;
G11C 8/10 20130101 |
Class at
Publication: |
711/103 ;
711/105; 711/154; 711/E12.008 |
International
Class: |
G06F 12/00 20060101
G06F012/00 |
Claims
1. A method of operation within an integrated-circuit memory
device, the method comprising: retrieving a first data value from
an address-specified location within a memory core of the memory
device in response to a memory access command; outputting the first
data value from the memory device in response to the memory access
command; and storing a second data value in the address-specified
location within the memory core in response to the memory access
command.
2. The method of claim 1 wherein retrieving a first data value from
an address-specified location within a memory core of the memory
device comprises retrieving a first data value from a column of
sense amplifiers within a sense amplifier bank of the memory
device.
3. The method of claim 2 further comprising transferring data from
a row of storage cells to the sense amplifier bank in a row
activation operation carried out prior to receipt of the memory
access command, wherein the row of storage cells forms part of a
storage array within the memory core.
4. The method of claim 2 wherein storing a second data value in the
address-specified location within the memory core comprises storing
the second value within the column of sense amplifiers.
5. The method of claim 1 wherein outputting the firs data value
from the memory device in response to the memory access command
comprises outputting the first data value onto a data path external
to the memory device.
6. The method of claim 1 further comprising modifying the first
data value in response to the memory access command to generate the
second data value.
7. The method of claim 6 wherein modifying the first data value
comprises incrementing the first data value in response to the
memory access command such that the second data value is an
incremented version of the first data value.
8. The method of claim 6 wherein modifying the first data value
comprises performing an logical operation in which the first data
value constitutes a first operand and a third data value
constitutes a second operand.
9. The method of claim 8 further comprising receiving the third
data value from a register within the memory device.
10. The method of claim 8 further comprising receiving the third
data value via an external data path.
11. The method of claim 10 wherein receiving the third data value
via an external data path comprises receiving the third data value
via the external data path concurrently with receiving the memory
access command via an external command path.
12. The method of claim 8 wherein the logical operation comprises
an arithmetic operation.
13. The method of claim 1 further comprising receiving the second
data value via an external data path prior to outputting the first
data value from the memory device, and wherein outputting the first
data value from the memory device comprises outputting the first
data value via the external data path.
14. The method of claim 1 further comprising comparing the first
data value with the second data value to generate a comparison
result, and wherein storing the second data value in the
address-specified location within the memory core comprises
conditionally storing the second data value in the
address-specified location according to the comparison result.
15. The method of claim 14 wherein conditionally storing the second
data value in the address-specified location according to the
comparison result comprises storing the second data value in the
address-specified location only if the comparison result indicates
that an aspect of the second data value exceeds a corresponding
aspect of the first data value.
16. An integrated-circuit memory device comprising: a memory core;
and core access circuitry to retrieve a first data value from an
address-specified location within the memory core in response to a
memory access command and to store a second data value in the
address-specified location within the memory core in response to
the memory access command.
17. The integrated-circuit memory device of claim 16 wherein the
core access circuitry comprises: control logic to receive the
memory access command and a corresponding memory address and to
enable access to the address-specified location in response to the
memory access command and corresponding memory address; and data
input/output (I/O) circuitry to receive the first data value from
the address-specified location in the memory core via the control
logic and to output the first data value from the
integrated-circuit memory device.
18. The integrated circuit device of claim 17 wherein the data I/O
circuitry comprises a data receive circuit to receive the second
data value via an external signaling path in response to the memory
access command.
19. The integrated circuit device of claim 17 wherein the data I/O
circuitry comprises a data receive circuit to receive a third data
value via an external signaling path in association with the memory
access command, and modify logic circuitry coupled to receive the
third data value from the data receive circuit and the first data
value from the memory core, the modify logic circuitry including
circuitry to generate the second data value using the first and
third data values.
20. The integrated-circuit memory device of claim 17 wherein the
data I/O circuitry comprises modify logic circuitry coupled to
receive the first data value from the memory core and having
circuitry to generate the second data value by modifying the first
data value.
21. The integrated-circuit memory device of claim 17 wherein the
data I/O circuitry comprises a data receive circuit to receive the
second data value via an external signaling path in response to the
memory access command.
22. The integrated-circuit memory device of claim 21 further
comprising modify logic coupled to receive the second data value
from the data receive circuit and the first data value from the
memory core, the modify logic circuitry including circuitry to
compare the first and second data values to generate a comparison
result, and to conditionally enable the second data value to be
stored in the address-specified location within the memory core
depending on the comparison result.
23. The integrated circuit memory device of claim 17 further
comprising a register to store the second data value prior to
receipt of the memory access command.
24. The integrated-circuit memory device of claim 16 wherein the
memory core comprises plurality of dynamic random access memory
cells.
25. The integrated-circuit memory device of claim 16 wherein the
memory core comprises a plurality of flash memory cells.
26. An integrated-circuit memory device comprising: a memory core;
means for retrieving a first data value from an address-specified
location within the memory core in response to a memory access
command; means for outputting the first data value from the memory
device in response to the memory access command; and means for
storing a second data value in the address-specified location
within the memory core in response to the memory access
command.
27. A manufacture comprising one or more computer-readable storage
media, the computer-readable storage media having information
embodied therein that describes a physical implementation of an
integrated circuit device, the information including descriptions
of: a memory core; and core access circuitry to retrieve a first
data value from an address-specified location within the memory
core in response to a memory access command and to store a second
data value in the address-specified location within the memory core
in response to the memory access command.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to the field of data
processing, and more particularly to data storage and manipulation
within a data processing system.
BACKGROUND
[0002] The ever-increasing gap between processor performance and
memory bandwidth is reflected in the growing timing penalty
incurred when a processor must fetch data from operating memory.
While processor-stalls (awaiting data retrieval) and architectural
remedies (e.g., cache memories) are costly enough in
single-processor systems, such costs tend to be multiplied in
multi-processor systems (including multi-core processors),
particularly where multiple processors or processor cores share
storage locations (e.g., memory). In that case, modification of the
shared data by one of the processors generally requires coherency
control--interprocessor communication or other high-level
coordination such as "locks" or "semaphores" to exclude the other
processors from accessing the potentially-stale shared data while
the data-modifying processor carries out the multiple steps
required to fetch the shared data from the operating memory, modify
the data, and then write the modified data back to the operating
memory. In general, any of the excluded processors that requires
access to the shared data must await notification that the
exclusive access is complete.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The present invention is illustrated by way of example, and
no way of limitation, in the figures of the accompanying drawings
and in which like reference numerals refer to similar elements and
in which:
[0004] FIG. 1A illustrates an embodiment of a data processing
system capable of carrying out access-protected data modification
operations, referred to herein as "atomic" memory operations;
[0005] FIGS. 1B-1F illustrate the flow of data in a number atomic
memory operations supported by the atomic memory device and atomic
memory controller of FIG. 1A;
[0006] FIGS. 1G and 1H illustrate the flow of data in a umber
simplex memory operations supported by the atomic memory device and
atomic memory controller of FIG. 1A;
[0007] FIG. 2 illustrates an embodiment of an atomic memory device
in greater detail;
[0008] FIG. 3 illustrates an embodiment of a modify logic circuit
that may be used to implement the modify logic shown in FIG. 2;
[0009] FIG. 4 illustrates a table of operations that may be
initiated and controlled by the modify controller of FIG. 3;
[0010] FIG. 5 illustrates a generalized and exemplary operation of
an atomic memory device in response to receipt of a memory access
command; and
[0011] FIG. 6 is a timing diagram illustrating signal timing during
an exemplary duplex operation within the atomic memory device of
FIG. 3.
DETAILED DESCRIPTION
[0012] Memory devices having circuitry to perform data modification
operations within the time interval generally required for data
access are disclosed in various embodiments. In general, by hiding
the data modification operation under or within the memory access
time, exclusive access to the data is established by the memory
access processes within the memory device itself, thus obviating
costly and inefficient exclusivity control mechanisms within the
processor(s), memory controller or other upstream circuitry. In
several single integrated circuit embodiments presented below, an
input-output pipeline of an integrated circuit memory device
includes capability to perform multi-step operations and to write
data back into the same or different memory cells; because these
operations are performed by the input-output pipeline (which
generally can only be used by one requestor at a time), a lock can
be effectively established without using complicated software
mechanisms or multi-processor communications.
[0013] A hypothetical illustration is presented with an example of
two users, each having a separate workstation and desiring to
update a shared financial account database having an entry of $100.
Each user's workstation might read the entry in-question ($100),
and each user might desire to update the account to add different
increments (e.g., to add $20 in the case of the first user, and to
add $50 in the case of the second user). The use of software locks
in this situation would imply unavailability of the entry or of
related processing to one user until the other user is finished;
the failure to use locks might imply that the second use o access
the entry might read a stale entry ($100) and then overwrite that
stale entry with an update (e.g., $150) of stale info, resulting in
an incorrect entry (e.g., $150 overwriting the first user's entry
$120 when the correct value should be $170).
[0014] FIG. 1A illustrates an embodiment of a data processing
system 100 capable of carrying out access-protected data
modification operations--that is, data modification operations that
are carried out concurrently or coextensively with a memory access
operation and thus protected from undesired intervening access by
timing restrictions imposed by the memory access itself. Such
compound memory operations (i.e., involving data retrieval from one
or more memory cores as well as logical, arithmetic, exchange or
other operations with respect to the retrieved data) are referred
to herein generally as "atomic" operations as they are indivisible
from the standpoint of competing memory requestors. Accordingly, as
the atomic character of such compound operations is enforced
(effected) by circuitry within individual memory devices that
populate the memory subsystem, and issuance of specialized "atomic"
memory access commands (or requests or instructions) by a memory
controller, such memory devices are referred to herein as "atomic"
memory devices and the memory controller as an "atomic" memory
controller. Thus, the memory subsystem of FIG. 1A includes an
atomic memory controller 101 that responds to memory access
requests (issued via a host request path, "HostReq") from one or
more processors 102 or other host devices running one or more
threads; each "atomic operation" is effected by issuing
corresponding command and address information to one or more atomic
memory devices 103 via command/address path 110 ("C/A"). In the
case of a host-write request, write data is output from the host
processor 102 to the atomic memory controller 101 via a host data
path ("HostData") and then from the atomic memory controller 101 to
the atomic memory devices 103 via memory data path 112 ("Data").
Conversely, in the case of a host-read request, read data is output
from one or more of the atomic memory devices 103 to the atomic
memory controller 101 via the memory data path 112, and then from
the atomic memory controller 101 to the requesting host 102 via the
corresponding host data path.
[0015] With regard to the memory subsystem topology, any number of
atomic memory devices 103 may be coupled to the atomic memory
controller 101 in any combination of point-to-point and multi-drop
signaling paths. In one embodiment, for example, the atomic memory
devices 103 are organized into one or more memory ranks (i.e.,
selected as a unit via one or more chip-select lines or other
selection mechanisms) with each atomic memory device 103 of the
memory rank being coupled to the atomic memory controller 101 via a
common command/address path 110 and via respective
(dedicated-per-memory-device) memory data paths 110. By this
arrangement, the memory devices of a given rank may be selected as
a unit (e.g., via a shared chip-select line or other device
selection mechanism) to receive the same memory access command and
memory address, and to respond to the common command/address by
receiving or outputting respective portions of the overall data
word (via dedicated memory data paths) being transferred between
the rank of atomic memory devices 103 and the atomic memory
controller 101. In alternative embodiments, separate
command/address paths 110 may be provided to enable selection of
atomic memory devices either as a rank or individually (or in
sub-groups within a rank), and/or multiple atomic memory devices
103 may be coupled to a memory data path 110 (or to each memory
data path 110 in system 100) in a multi-drop arrangement.
[0016] Still referring to FIG. 1A, each of the atomic memory
devices 103 includes core access circuitry 107 to enable access to
a memory core 105 formed by one or more arrays of storage cells.
The storage arrays of the memory core 105 may be populated by
virtually any type of storage cells including for example and
without limitation, volatile or non-volatile memory; for example,
the storage cells may include static random access memory (static
RAM or SRAM) cells, dynamic RAM (DRAM) cells, charge-trapping cells
such NAND or NOR flash memory cells, phase-change memory cells,
ferro-magnetic memory cells or any other storage cell technology
that permits storage and retrieval of digital data. Further, the
memory core 105 may include various signal lines and circuitry to
enable access to the underlying storage cells such as, for example
and without limitation, word lines to enable access to
address-selected rows of storage cells, bit lines to convey data
signals between word-line-selected storage cells and sense
amplifiers or like circuitry, and sense amplifiers themselves for
sensing (and/or latching) signals output from the selected cells
during data retrieval (read) operations and for driving signals
back to the selected cells during write or refresh operations. For
purposes of clarity and definitiveness, atomic memory devices are
presented in embodiments below as having a DRAM core and
occasionally referred to as atomic DRAMs. In all such embodiments,
data storage technologies other than DRAM may be used in accordance
with the innovations and improvements disclosed herein, with
commensurate changes in the memory core 105, core access circuitry
107, atomic memory controller 101 and interconnection topology.
[0017] Continuing with the exemplary atomic memory device 103 shown
in FIG. 1A, core access circuitry 107 includes control logic
circuitry 109 coupled to receive command and address information
via the command/address path 110 (which may be formed by separate
command and address paths, or by a single signaling path that is
time-multiplexed with command and address information) and data
input/output (I/O) circuitry 115 to manage data transfer between
the memory core 105 and the external data path (i.e., memory data
path 112). The control logic circuitry 109 ("control logic" for
short) responds to incoming commands and addresses by controlling
operation of the memory core 105 (initiating row and column
decoding operations, sense operations, refresh operations,
precharge operations, programming operations, erase operations,
etc.) and also controlling operation of the data I/O circuitry 115.
In particular, the control logic circuitry 109 may manage the
timing of data reception during memory write operations (and atomic
memory operations that involve data storage), enabling the data I/O
circuitry to begin data sampling incoming data (e.g., write data,
swap data and/or operand data as discussed below) from the external
data path at a predetermined time with respect to registration of a
corresponding memory command and to latch the incoming data in one
or more registers or buffers that form an interface to the memory
core 105. Similarly, control logic 109 may manage the timing of
data transmission during memory read operations, enabling the data
I/O circuitry 115 to begin unloading read data from the memory core
interface and outputting the read data onto the external data path
at a predetermined time with respect to registration of a memory
read command (or a command to perform an atomic operation that
returns data to the host requestor). Though not specifically shown,
various timing signals including clock and/or strobe signals (i.e.,
signals that transition to indicate the presence of valid data) may
be received or generated within the atomic memory device 103 and
used to coordinate data sampling, transmission operations as well
as internal operations within the control logic 109, data I/O
circuitry 115 and/or memory core.
[0018] In contrast to conventional memory devices, the atomic
memory device 103 includes circuitry to execute the above-described
data modification operations concurrently with data retrieval. More
specifically, the control logic 109 includes circuitry that
responds to atomic operation commands (i.e., commands to execute
specified atomic operations) as well as non-atomic memory read and
write commands and row activation commands, precharge commands,
refresh commands, program commands, erase commands, and so forth as
necessary to manage the underlying memory technology). Further, as
shown in FIG. 1A, the data I/O circuitry 115 includes modify logic
circuitry 117 ("modify logic" for short) to enable modification and
write-back of retrieved data as it is en route to its external
destination, if any. In one embodiment, for example, the modify
logic 117 is coupled between internal serial data lines 131, 133
used to convey outgoing, (read) and incoming (write) data between
data I/O sampler and driver circuits (121 and 123, respectively)
and the memory core interface. As retrieved data is shifted bit by
bit onto the outgoing serial data line 133 (i.e., away from the
memory core 105), the serial data bits may be received within and
operated upon by the modify logic 117 in accordance with a
specified modify-operation 128 to produce modified data which is,
in turn, shifted bit by bit onto the incoming serial data line 131
(i.e., toward the memory core) and thus written back to the memory
core 105. Because the overall data modification and write-back time
may be completely or at least substantially hidden under the data
retrieval time itself (e.g., within the column access time or
column access cycle time of a memory device), the inherent timing
restrictions imposed by the memory core technology serve to prevent
undesired access to the modified data prior to its storage within
the memory core 105 (including storage within the sense amp bank of
the memory core, if not within the more remote storage cells
themselves) and thus ensure coherency without need for coherency
mechanisms within the host requestor or memory controller. That is
to say, a data read and write (e.g., read-modify-write) operation
performed in the memory device is performed within the input-output
path in a manner that it (a) is performed far more quickly than
lock mechanisms (where a memory lock is established through
software or hardware during processing by a remote controller and
(b) cannot be interfered with by another incoming operation.
Returning to the hypothetical illustration presented above,
relating to a financial account entry, the memory device may employ
a single read-modify-write operation such that an operation to
write an updated value into memory (e.g., $120) can be performed in
a single command, such updates can never be commenced for data that
is stale.
[0019] FIGS. 1B-1F illustrates the flow of data in a number atomic
memory operations supported by the atomic memory device 103 and
atomic memory controller 101 of FIG. 1A. Exemplary operations that
can be performed include operations that combine a data access with
one or more logical operations, for example, increment operations,
decrement operations, inversion, shift and similar operations.
Other operations may combine multiple memory access operations,
such as for example a swap operation where data in one memory
location is swapped with data from another memory location or with
data provided by a memory command.
[0020] Starting with FIG. 1B, in a read/modify operation, data is
retrieved as part of a memory read operation, modified within the
modify logic 117 in accordance with a modify-operation 128 ("op")
specified by the control logic (and thus by the atomic command from
the atomic memory controller) and written back to the memory core
105 in place of the retrieved data.
[0021] In FIG. 1C, a similar atomic operation is performed except
that, instead of a unary operation in which the read data
constitutes the sole operand, a binary (two-operand) operation is
performed in accordance with the specified modify-operation 128
using the read data as a primary operand and an internally or
externally sourced data value (shown in FIG. 1C as "operand" 140)
as the secondary operand. As discussed below, such a sourced
operand may be a value previously retrieved from the memory core
105 and stored within an operand register, a value stored within an
operand register as part of a memory-controller-instructed
register-write operation, a carry-bit from another memory device
e.g., from an adjacent rank) or any other operand data source. An
externally-sourced operand (e.g., a value to be loaded into an
operand) may be provided, for example, via the external data path
(i.e., memory data path 112 of FIG. 1A) in generally the same
manner (though necessarily the same command-relative timing) as
write data. Alternatively, on externally-sourced operand may be
provided via the command/address path (e.g., time-multiplexed with
other information transmitted thereon) or any other signaling
connection to the atomic memory device (e.g., an out-of-band
transmission channel such as common mode signaling over a
differential data link, low-speed signal channel used to initialize
the memory system, etc.). As a specific example of an
externally-sourced operand, an operand-load instruction and operand
value may be provided from atomic memory controller 101 to atomic
memory device 103 via the C/A and data paths, respectively (or via
either path individually, or via any other in-band or out-of-band
signaling path). The control logic 109 within the atomic memory
device 103 responds to the operand-load instruction by enabling the
specified operand register to be loaded with the incoming operand
value. In addition to the techniques identified above, a carry-bit
or other operand or result of an operation within modify logic 117
may be output from a memory device (or rank) as shown at 141 ("op
result") and provided to another memory device or to a memory
controller, to indicate overflow/underflow or other results of such
operations.
[0022] FIG. 1D illustrates an atomic data-exchange or data-swap
operation that may be performed within the memory device
architecture of FIG. 1A. Although similar to the binary operation
shown in FIG. 1C, instead of performing a modification of the read
data value, the read data is conditionally or unconditionally
swapped with a swap data value ("swap data") via multiplexing
circuitry 151. That is, the swap data value is conditionally or
unconditionally written back to the memory core 105 in place of the
read data, and the swap data may also be conditionally or
unconditionally returned to the memory controller (and thus the
host requestor) to signify the swap result. As with the secondary
operand in a binary operation, the swap data value may be
internally or externally sourced (i.e., provided by a source within
or outside the atomic memory device, respectively). In an
unconditional swap, referred to herein simply as a swap operation,
the swap data value is written back to the memory core in place of
the read data value (i.e., overwriting the read data value) while
the read data value is returned to the memory controller (and thus
to the host requestor). In a conditional swap, modify logic 117
evaluates the read data and/or swap data and conditionally
exchanges (swaps) the read data and swap data depending on the
evaluation result. As an example, in a particular form of
conditional swap referred to herein as a compare-and-swap, the
modify logic compares the swap data and read data to determine
which is more superlative (greater than, less than, higher
magnitude, more `1` or more `0` bits, etc.), writing the swap data
back to memory core 105 only if it is the more superlative value.
Alternatively (or in response to a different type of conditional
swap command), the read data alone or the swap data alone may be
evaluated (or may be evaluated with respect to a register-sourced
condition or compare value as shown by dashed arrow 142 in FIG. 1D)
to determine whether the exchange condition is satisfied (e.g.,
determining whether a predetermined characteristic of the read data
or swap data is met (e.g., more `1`s than `0`s) or whether read
data or swap data exceeds (in any sense) the register-sourced
compare value). Whichever data evaluation is performed, if the swap
condition is satisfied, the read data may be returned to the
swap-data source (e.g., internal register or memory controller)
with or without also writing back the read data to memory core 105
(e.g., no data change will occur, write-back may be suppressed or
otherwise omitted) and, conversely, if a swap does occur (i.e.,
exchange-condition satisfied), the swap data may be returned to the
swap-data source. Alternatively, or as part of a different
conditional swap command, the read data may be returned regardless
of whether the exchange condition is satisfied.
[0023] Still referring to FIG. 1D, in a more general conditional
operation, the read data may be conditionally modified according to
an evaluation of the read data, externally sourced data and/or
internally-sourced (e.g., register-supplied) data, with the
conditionally modified data written back to the memory core 105
and/or returned to the host requestor. Also, a combination of
conditional modification and conditional swap may be carried out.
As an example of a unary conditional operation, a read data value
may be evaluated to determine whether it has more `0` bits than `1`
bits (or vice-versa) and, if so, complemented by the modify logic
to generate, as a modified data value, an inverted read data value
that is written back to the memory core (and optionally transmitted
back to the operation requestor). As an example of a binary
conditional operation, the read data value may be compared with an
externally sourced data value, with the more superlative value
(read data value or externally sourced value) modified in some way
(e.g., incrementing a counter field within the more superlative
value to indicate the number of comparisons the more superlative
value has won) before writing the more superlative value back to
the memory core 105. More generally, virtually any useful
conditional exchange and/or conditional modification may be
executed within the modify logic 117 with optional return of the
original, modified and/or superlative data to the memory core or to
the memory controller.
[0024] FIG. 1E illustrates a special case of a modification
operation in which the modified data is returned to the memory
controller instead of the read data value. As discussed, the read
data value may be absolutely (i.e., in all cases) modified or
conditionally modified within the modify logic 117.
[0025] FIG. 1F illustrates another special case in which the read
data is not returned o the memory controller in either its original
or modified form, while the data modified or conditionally modified
by modify logic 117 is written back to the memory core 105.
[0026] Reflecting on the atomic operations described in reference
to FIGS. 1B-1F, it can be seen that each generally involves
bi-directional data transfer with respect to the memory core 105
(including conditional bi-directional transfer as the write-back
may be conditionally omitted or suppressed as discussed above).
Accordingly, such operations are occasionally referred to herein as
"duplex" operations to distinguish them from "simplex" operations
in which data flow is uni-directional with respect to the memory
core. While such duplex operations may be implemented with any
underlying memory technology as discussed above, in memory
technologies that exhibit a relatively long write latency (e.g.,
NAND-based flash memory, in which an entire physical page may be
written at once), a number of implementation choices may be
provided with regard to duplex operation timing. For example and
without limitation, an internal write cache may be provided to
buffer data to be written as part of a duplex operation, thereby
enabling data write-back to be completed quickly within the
write-cache. Transfer from the write-cache to the memory core may
then occur over a longer time interval (e.g., as required by the
underlying memory technology) and potentially at a later time,
after multiple updates to the contents of the write cache.
[0027] Examples of simplex operations, which are also supported by
the atomic memory device 103, include memory read operations and
memory write operations as illustrated in FIGS. 1G and 1H. As
shown, operation of the modify logic 117 is disabled (an/or the
internal read-data path/write-data path is decoupled from the
modify logic 117 as indicated by the `X`) so that read data flows
uni-directionally from the memory core 105 to the memory controller
in a memory read operation (FIG. 1G) and write data flows
uni-directionally from the memory controller to the memory core 105
in a memory write operation (FIG. 1H).
[0028] In the various embodiments described above, a memory device
architecture supporting atomic operations within the device
input-output path may receive a superset of commands including both
commands for atomic operations as well as more traditional
commands, such as those depicted with reference to FIGS. 1G-1H.
[0029] FIG. 2 illustrates an embodiment of an atomic memory device
180 in greater detail. As with the generalized atomic memory device
of FIG. 1A, atomic memory device 180 includes a memory core 181,
control logic circuitry 183 and data I/O circuitry 185. For
purposes of explanation only, the memory core 105 is assumed to be
a DRAM core having one or more arrays of DRAM cells and
corresponding sense amplifier banks 191 that are accessed in
response to row and column commands received via command path 214
and corresponding row and column addresses received via address
path 216 (the command and address paths collectively forming
command/address path 210). Incoming memory access commands are
received within a command decoder 197 (e.g., a state machine,
sequencer or other decode-and-control circuitry) which issues
corresponding control signals to address decoding circuitry and to
data I/O circuitry 185 to carry out the requested operation. Upon
receiving a row activation command (i.e., command to transfer an
address-selected row of data to the sense amp bank), for example,
the command decoder 197 asserts a row-decode-enable signal
("rowdec_en") to row decoder 199 to enable the row decoder to
decode a row address received via the address path 216 and thereby
activate a word line coupled to an address-selected row of cells
within the memory core 181. The activated word line enables the
contents of the corresponding storage cells (i.e., the storage
cells coupled to the word line) to drive respective bit lines (or
pairs of bit lines) which are sensed by the bank(s) of sense
amplifiers 191. Through this "row activation" operation, the
contents of a storage row may be sensed and latched within the
sense amplifier bank(s) 191, thus opening a "page" of data that may
be accessed via column access (read and write) operations.
Accordingly, upon receiving a column access command (i.e., command
to read or write a column of data within a previously activated
row, and thus a row of data within the sense amplifier bank), the
command decoder 197 issues a column-decode-enable signal
("coldec_en") to enable the column decoder 201(or column
multiplexer) to decode a column address received via the address
path 216 and, by that operation, form a multiplexed signal
conduction path between an address-selected column of data within
the sense amplifier bank(s) 191 and a parallel data path referred
to herein as the core data path 260.
[0030] When an atomic command is received within the command
decoder 197, the command decoder issues decode-enable signals in
accordance with the atomic operation requested (e.g.,
column-decode-enable if column data is to be retrieved as part of
the atomic operation) and also outputs an operation-select
("opsel") value to one or more modify logic circuits 251 included
within the data I/O circuitry 185. The command decoder 197 may
additionally output numerous signals and commands to control data
sample timing (i.e., data reception), data transmission timing,
data buffering, internal data transfer between component circuit
blocks, specialized program/erase operation (e.g., in the case of
NAND or NOR flash or similar memory), maintenance operations (e.g.,
self-refresh, auto-refresh, signaling calibration, etc.) or any
other control function within the atomic memory device 181. Also,
the command decoder 197 may include or enable access to various
status registers, control registers and data registers to allow
device configurability. In one embodiment, for example, support for
atomic operations may be disabled through host-instructed
programming of a mode register 218 within the command decoder, thus
enabling the atomic memory device to mimic the behavior of legacy
memory devices (i.e., in terms of operational timing and/or manner
of decoding incoming commands, etc.). As another example, one or
more operand registers 216 may be provided to provide operand(s) to
the data modify logic 251. In one implementation, for example, a
solitary programmable operand register 216 is used to provide
operand data to each of the modify logic circuits 251 within the
data I/O circuitry 185. In an alternative embodiment, a bank of
programmable operand registers 216 are provided, with one or more
of the operand registers 216 being selected in accordance with an
incoming atomic memory command to provide operand data ("operand")
to the modify logic circuits 251. All such mode registers 218 and
operand registers 216 may be one-time or run-time programmable. In
the case of run-time programmable registers, for example, the mode
register 218 may be programmed in response to host instructions
(e.g., provided via the memory controller) during system startup to
establish an initial operating configuration, and the operand
register(s) 216 may be programmed during startup and as needed
thereafter to provide operands for use in atomic operations. Values
programmed within the mode registers 218 and operand registers 216
may be transferred to the atomic memory device 180 via any or all
of the signal paths shown (address 216, command 214, data 212
(DQ)), or via other signaling paths such as low-bandwidth control
path, out-of-band signaling channel, etc.).
[0031] In one embodiment, the data I/O circuitry 185 includes a
number of I/O bit-slice circuits 225 each coupled to a respective
data link of the external data path via a pin (or pair of pins in a
differential signaling implementation) or other integrated-circuit
interconnect. Referring to the detail view of I/O bit-slice circuit
225.sub.0 ("I/O slice 225.sub.0" for short), the on-chip portion of
the incoming data link is coupled to a signal transceiver formed by
sampling circuit 231 and output driver 233. In one embodiment, data
reception within the sampling 231 is timed by transitions of a
receive timing signal (which may be a strobe signal or clock signal
received in association with the incoming data signal, or an
internally synthesized signal) so that the sampling circuit outputs
a serial stream of received data bits onto write-data-in ("wdi")
line 232. As shown, the write-data-in line 232 extends into the
modify logic 251 where it is coupled to one or more modify units
259 and also to a write-data-out ("wdo") multiplexer 255 or other
signal switching or selection logic). As discussed below, the wdo
multiplexer 255 selects either the wdi line 232 or an output of the
modify units 259 to drive a serial write-data-out line 234 ("wdo
line"), and thus enables passage of write data to the memory core
181 in a simplex write operation, or passage of swap data or
modified data to the memory core 181 in a duplex (atomic)
operation.
[0032] In one embodiment, data to be written to the memory core 181
is converted from serial to parallel form within each of the I/O
bit-slices 225, thus enabling the core cycle frequency (e.g.,
column-access cycle time (column cycle time), core clock cycle, or
other cycle time of the memory core 181) to be a fraction of the
data I/O frequency. That is, a deserializing circuit 241 ("deser")
is provided at the interface between the core data path 261 and the
data I/O circuitry 185 to convert serial data conveyed on the wdo
line 234 to parallel data for conveyance on core data path 260 and
storage within memory core 181. In the particular implementation of
FIG. 2, for example, serial data on the wdo line 234 is shifted bit
by bit into deserializer 241 at the data I/O frequency (i.e.,
1/(bit-time on data path)) and then framed and transferred out of
the deserializer and onto core data path 260 at a word rate (e.g.,
the ratio of serial data frequency to core frequency), 1/8.sup.th
or 1/16.sup.th the data I/O frequency. For example, after serial
shifting of each group of sixteen bits into a shift register of
deserializer 241, the core timing signal can be transitioned to
transfer the 16-bit data slice within the shift register, in
parallel, onto core data path 260. In the exemplary embodiment of
FIG. 2, the atomic memory device 180 has a 32-bit wide data
interface (i.e., to interface to a 32-bit wide external data path)
and enables operation of all the I/O bit slice circuits
225.sub.0-225.sub.31 simultaneously (i.e., each circuit receives
data in parallel) so that a core data word formed by a total of
32*16=512 bits is transferred from the data I/O circuitry 185 to
the core data path 260 at the conclusion of each core framing
interval (core cycle) as marked by a transition of the core timing
signal. The core data word is conveyed via the column decoder
circuitry 201 to the appropriate 512 bit column of sense amplifiers
with sense amplifier bank(s) 191, overwriting the contents therein
to complete a column write operation. Thereafter, after some number
of memory write/read operations directed to the open page of data
(i.e., contents of a storage row present in the sense amplifiers)
is completed, a precharge operation may be carried out to close the
open page. That is, if the page of data within the sense amplifier
bank(s) 191 (which may include thousands or more 512-bit columns)
has not already been written back to the corresponding row of
storage cells, write-back to the storage cells is completed, the
corresponding word line deactivated, and the bit lines and sense
amplifiers conditioned in preparation for the next row activation
operation.
[0033] Still referring to FIG. 2, data flow in a simplex memory
read operation is essentially the reverse of that described above
in connection with a simplex memory write. That is, an
address-selected column of data. is output from the memory core 181
(i.e., from sense amplifier bank(s) 191 in a DRAM embodiment) to
the core data path 260 via the column decoder 201. Serializers 243
("ser") within respective I/O bit slice circuits 225 then operate
in reverse-manner to the deserializers 241 described above, each
converting a respective parallel set of 16 bits into a
corresponding stream of sixteen serial bits that are output onto a
read-data-in line 236 (the "rdi" line). The rdi line 236 is coupled
to the modify units 259 within the modify logic 251 and to a
read-data-out ("rdo") multiplexer 257. The rdo multiplexer 257 also
receives a data output from the modify units 259 and operates in
response to a control signal to pass either the serial data stream
supplied via the rdi line 236 (i.e., the "retrieved data" or "read
data") or modified data from the modify units 259 to a
read-data-out line 238 (the "rdo" line). The rdo line 238 conveys
the serial stream of retrieved or modified data to output driver
233 which drives the data serially onto a respective one of the
signaling links of the external data path 212.
[0034] Still referring to FIG. 2, the above-described relationship
between the data I/O frequency and core cycle interval is shown at
262 and 264. That is, during each core cycle interval in which data
is being written into and/or retrieved from the memory core 181,
sixteen data bits are transmitted serially via the wdo line 234
and/or the rdi line 236. During that same core cycle interval
(though potentially offset to account for transfer delays within
various circuits of the data I/O circuitry and/or core memory), a
512-bit core data word is transferred between the memory core and
the core interface.
[0035] Reflecting on the atomic memory of FIG. 2, it should be
noted that the specific numbers of bits, bit ratios, frequency
ratios and so forth are provided for purposes of example only. In
all such cases, different numbers of bits and ratios may apply.
Further, while specific circuit blocks have been shown, numerous
other circuit blocks may also be provided (and the functions of the
circuit blocks shown and described organized differently with
regard to such other circuit blocks) without departing from the
scope of the present disclosure.
[0036] FIG. 3 illustrates an embodiment of a modify logic circuit
280 that may be used to implement modify logic 251 of FIG. 2. The
modify logic circuit 280 includes a modify controller 281,
write-data-out (wdo) and read-data-out (rdo) multiplexers 285 and
287, and a set of one or more modify units 293.sub.0-293.sub.N-1
(collectively, "293"). The modify controller 281 responds to
incoming operation-select signals 128 ("opsel") by issuing
multiplexer-control signals, wdo_sel and rdo_sel, to the wdo and
rdo multiplexers 285 and 287, respectively, and by asserting
enabling one or more modify-enable signals (en_0, . . . , enN-1) to
enable corresponding modify units 293 to perform evaluation and/or
modification operations. The modify controller 281 may also receive
one or more operation-result signals (res_0,res_1, res_N-1) from
the modify units 293 and use those results in whole or part in
generating the enable signals and multiplexer control signals. For
example, in a compare-and-swap operation, one of the modify units
293 may perform a data comparison and provide the comparison result
to the modify controller 281 to enable determination of the wdo
multiplexer setting (and/or rdo multiplexer setting). Although not
specifically shown, the modify controller 281 may be clocked or
otherwise advanced between states in response to a clock signal
(e.g., operating at the data I/O frequency or a subdivided
frequency thereof such as the core clock cycle frequency) and may
be implemented by any combination of combinatorial and state
management logic. For example, in one embodiment the modify
controller 281 is implemented as a finite state machine, though an
instruction sequencer or even purely combinatorial implementation
may be provided in alternative embodiments. In these embodiments,
the modify controller 281 may include sets of parallel logic, one
for each slice (i.e., for each modify unit 293.sub.0-293.sub.N-1)
for processing each slice in parallel.
[0037] Each of the modify units 293 or any subset thereof may be
coupled to the read-data-in line 236 to enable receipt of retrieved
serial data as necessary to carry out the operation specified by
opsel signal 128. Each of the modify units 293 or a subset thereof
may also be coupled to the write-data-in line 232 to enable receipt
of externally received serial data which may be write-data, swap
data, an externally sourced operand or any other externally
supplied information having useful application within the modifv
logic 280. The modify units 293 or any subset thereof may be
coupled to receive an operand from an operand register via operand
path 141 as discussed above. Also, while a solitary operand path
141 is shown, multiple operand paths may be provided to provide
multiple operands to a given modify unit 293 and/or to provide
respective operands to different modify units. Each of the modify
units 293 or any subset thereof may also include a select input
(s0, s1, . . . , sN-1) coupled to receive a respective enable
signal from the modify controller 281, a result signal output
(res_0, res_1, resN-1) to deliver an operation-result signal to the
modify controller 281, and a serial-data-output coupled to a
modified-data line 284 to deliver modified data serially thereto.
The modified-data line 284 conveys modified data to the wdo
multiplexer 285 to enable the modified data to be written back to
the memory core, and also to the rdo multiplexer 287 to enable the
modified data to be output from the atomic memory device via the
external data path, both as discussed above.
[0038] Still referring to FIG. 3, any number of modify units 293
may be provided within modify logic 280, each to perform respective
modify functions or categories of modify functions. In the
particular embodiment shown, modify units representative of three
classes of modify-operations are depicted including a
unary-operation unit 293.sub.0, a binary-operation unit 293.sub.1
and an evaluation-operation unit 293.sub.N-1.
[0039] The unary-operation unit 293.sub.0 demonstrates signal
inputs and outputs representative of those used to enable unary
operations with respect to data retrieved from the memory core.
That is, the rdi line 236 is coupled to deliver the retrieved data
to the unary operation unit which, when enabled by the modify
controller 281 (i.e., en_0 asserted), carries out a specified unary
operation (or unary operation for which the underlying circuitry is
specifically designed) including for example and without
limitation, increment/decrement, complement, absolute value,
multiply or divide by fixed constant, exponent (raise to power),
root (square root, cubed root or the like), logarithm, table lookup
or any other single-argument function. Any result, res_0, generated
as part of the unary operation may be returned to the modify
controller 281 and/or stored within the modify unit 293.sub.0 or
elsewhere within the atomic memory device for later use. As an
example, a carry bit (i.e., overflow bit) or borrow bit (i.e.,
underflow bit) may be generated as part of an increment operation
or decrement operation and summed with/subtracted from a
subsequently retrieved data value to enable the increment/decrement
operation to be extended to data values greater than 16 bits i.e.,
enabling multiple retrieved data values to be processed as
constituent parts of a larger data value).
[0040] The binary-operation unit 293.sub.1 demonstrates signal
inputs and outputs representative of those used to enable binary
operations with respect to data retrieved from the memory core. In
the particular implementation shown, the binary-operation unit
receives the retrieved data via rdi line 236 and an operand
supplied via wdi line 232 as inputs. As discussed above, an operand
may additionally or alternatively be supplied via from one or more
operand registers within the atomic memory device via respective
operand paths 141. In any case, the binary operation unit 293.sub.1
carries out a binary operation (or ternary operation, quaternary
operation, etc. according to the number of supplied operands) when
enabled by the modify controller 281 and outputs resultant modified
data onto the modified-data line 284 and, optionally, a result
signal (e.g., borrow, carry, etc. onto the result signal line,
res_1. As with the unary-operation unit 293.sub.0, the
binary-operation unit 293.sub.1 may execute a selected, specified
operation (e.g., specified by the modify controller) or an
operation for which the underlying circuitry is specifically
designed. Examples of the binary operations performed include, for
example and without limitation, arithmetic operations (add,
subtract, multiply, divide), bit-wise logical operations (e.g., a
mask operation), Boolean operation; (AND, OR, XOR, . . . ),
two-dimensional table lookup, or any other multi-operand
functions.
[0041] Still referring to FIG. 3, the evaluation-operation unit
293.sub.N-1 may be viewed as a form of unary or binary operation
unit (according to the number of operands delivered) but is
presented separately to emphasize that at least some operations do
not require data output onto the modified-data line 284 (hence the
dashed interconnection of unit 293.sub.N-1 and modified-data line
284). That is, in one embodiment, the evaluation-operation unit
performs an evaluation of a retrieved, data value alone (unary
evaluation) or in combination with data received from an external
source and/or one or more operands (binary evaluation) and outputs
an evaluation-result signal on result line res_N-1 and/or an
evaluation data value (e.g., comparison winner) on modified-data
line 284. The result of the evaluation may be signaled to the
modify controller 281, for example, to enable the modify controller
281 to responsively control the wdo and/or rdo multiplexers 285,
287. As an example, if an evaluation result resolves to "TRUE" (as
signaled via res_N-1), then the wdi line 232 can be used to drive
wdo line 234, thereby enabling a data swap. Otherwise, if the
evaluation result resolves to "FALSE", a write-back operation can
be enabled, for example, by passing the retrieved data through the
evaluation-operation unit 293.sub.N-1 to the modified-data line 284
(e.g., as a comparison winner), and setting the wdo multiplexer 285
to couple the modified-data line 284 to the wdo line 234, thereby
routing the retrieved data onto the wdo line 234 for write-back to
the memory core. An example of the foregoing operation is an
operation to swap data only if the incoming value is greater than
the resident value in memory.
[0042] As an example of a unary evaluation, retrieved data may be
evaluated to determine whether a particular Boolean condition is
met (e.g., retrieved value evaluates to TRUE or FALSE) or whether
the retrieved data otherwise meets a predetermined condition, with
data exchange or other modify operations being performed with
respect to the same retrieved data value or a subsequently
retrieved data value according to the evaluation result. For
example, one conditional-increment function may increment data only
if not at a maximum (e.g., either a defined maximum of data or an
increment that avoids an overflow). In a binary evaluation, the
retrieved data value may be compared with the incoming operand data
(i.e., from register and/or external source) to generate an
operation result (e.g., inequality, match, logical combination of
retrieved value and operand satisfy a predetermined or
register-specified condition, etc.), with the operation result
again being used to enable conditional data exchange or other
modify operations with respect to the retrieved data value or a
subsequently retrieved data value.
[0043] As shown in detail view 301, each of the modify units 293
may be implemented by a modify circuit 305 and one or more delay
circuits, 307, 309, 311. The modify circuit 305 may include any
combinatorial or state-based logic for generating an operation
result and modified data in response to an enable signal (which may
be a multi-bit signal to instruct operation of one of multiple
possible operations supported by the modify circuit 305). In
general, such logic may be synthesized using circuit design tools
by specifying the operation to be performed (and thus the operation
result and the modified data output) with respect to the incoming
retrieved data and any operands. The delay circuits 307, 309, 311
may include hardwired or adjustable delay circuits (e.g., in
response to a register-programmed value, or a dynamic value provide
in connection with the operation-selection value) to delay
propagation of any or all incoming operands (ingress delay circuits
307, 309) to the inputs of the modify circuit 305, and/or to delay
propagation of the modified data to the modified-data line 284
(egress delay circuit 311) and/or to delay output of the operation
result (result delay circuit 313) to the modify controller. By this
arrangement, incoming operands may be provided to the modify
circuit 305 at an appropriate time or the modified data or an
operation-result may be driven at a desired time, thus enabling
coordination of various events within and external to the modify
logic 280 as well as pipelining of atomic operations. A designer
may utilize these features so as to tailor (e.g., optimize) traffic
flow through the input-output path of the memory device for the
atomic operations supported for the particular design.
[0044] FIG. 4 illustrates a table of operations (340) that may be
initiated and controlled by the modify controller of FIG. 3 in
accordance with the operation specified by the command decoder or
other control circuitry within the atomic memory device. Starting
with simplex memory read and simplex memory write operations shown
in the first two rows of table 340, because no data is being
conditionally or absolutely transmitted in a direction counter to
the simplex data flow, no modify unit is enabled. Instead, the
modify controller sets the rdo multiplexer to forward the retrieved
data ("read data") onto the read-data-out line in a simplex memory
read operation, and sets the rdi multiplexer to forward the
incoming write data onto the write-data-out line in a simplex
memory write operation. Although only two simplex data operations
are shown, other simplex operations may be performed, including
masked write, masked read, etc.
[0045] Turning to the duplex (atomic) operations listed in table
340, in a read/increment operation, the modify controller enables a
unary modify unit to carry out an increment operation with respect
to data retrieved from the memory core (the "read data), and sets
the rdo and wdo multiplexers to output the read data from the
atomic memory device and to deliver the modified data output from
the enabled modify unit (i.e., the incremented read data in this
example) to the memory core to be stored in place of the
just-retrieved read data. Thus, a memory read is performed
concurrently with incrementing the read data value, returning the
read data to the host requestor concurrently (i.e., at least partly
overlapping in time) with writing the incremented read data back to
the memory core. The increment/read operation is similar (i.e.,
unary modify unit also selected), except that the modified
(incremented) data is both written back to the memory core and
returned to the host requester.
[0046] Other examples of unary operations specifically shown in
table 340 include read/complement (read a data value and overwrite
it with its complement (inverted data value)) and complement/read
(overwrite the read data value with its complement and return the
complement value to the host). In all such cases, the write-back to
the memory core may be conditioned on evaluation of the retrieved
data and/or one or more operands. A 1's complement operation may
also be used (as opposed to a straight complement). As should be
apparent, although not specifically listed in table 340, numerous
other unary operations may be performed as discussed above.
[0047] Turning to examples of binary duplex operations that
reference register-sourced operands, in a read/add-offset
operation, the offset value within a register is added to a
retrieved data value to establish a variable+constant result that
may be unconditionally or conditionally written back to the memory
core. More specifically, a binary-operation unit that performs the
data+operand operation is enabled by the modify controller, and the
rdo and wdo multiplexers are set to pass the retrieved data value
to the rdo line and the modified data value to the wdo line,
respectively. In an add-offset/read operation, similar results are
obtained, but the modified data value (retrieved data value plus
operand) is returned to the host requestor instead of the read data
value. Read/subtract-offset and subtract-offset/read operations are
presented as additional examples of binary, register-based
operations. Though not specifically listed in table 340, numerous
other register-based binary operations may be performed.
[0048] The last set of exemplary operations presented in table 340
are binary operations that involve a host-supplied operand, that
is, binary duplex operations in which an externally-sourced operand
delivered via the wdi line is supplied to a modify unit together
with a retrieved data value. The specific examples presented
include swap, compare-and-swap, read/add-variable, and
add-variable/read. In the swap operation, no modify unit need be
enabled (as signified by the "N/A" or not-applicable designation)
and instead the modify controller sets the rdo and wdo multiplexers
to output the read data to the host requestor and to deliver the
swap data to the memory core to overwrite the just-retrieved read
data (thus effecting a swap operation). A compare-and-swap
operation is carried out similarly, except that the modify
controller enables a compare operation within an
evaluation-operation unit, and then sets the rdo and wdo
multiplexers in accordance with the compare result. In the
embodiment shown, for example, the wdo multiplexer may deliver
either the swap data or read data onto the wdo line (alternatively,
no data may be driven onto the wdo line if the swap data is not to
be written back to the memory core) and conversely deliver either
the read data or the swap data onto the rdo line according to the
comparison result. That is, if a swap is to be executed, the swap
data is delivered to the memory core and the read data is returned
to the host requestor. If a swap is not to be executed, the read
data is delivered to the memory core (or no write back is executed)
and the swap data is optionally returned to the memory requestor to
enable the memory requestor to ascertain the comparison result.
[0049] Turning to the read/add-variable operation, retrieved data
is returned to the host requestor and also added to an
externally-supplied operand to generate a sum that is written back,
as a modified data value, to the memory core. In the case of an
add-variable/read operation, the sum is both written back to the
memory core and returned to the host requestor. Again, though not
specifically listed in table 340, numerous other binary operations
that involve host-supplied operands may be performed. Also, as
described above, all such arithmetic operations, regardless of
their operand source, may be extended to enable operation with
respect to multiple retrieved data values through borrow or carry
storage or other state information as appropriate for the operation
performed.
[0050] FIG. 5 illustrates a generalized and exemplary operation of
an atomic memory device in response to receipt of a memory access
command as shown at 351. If no memory read is required (determined
in decision block 353), then the requested memory access is a
simplex write. Accordingly, the incoming write data value is stored
in the memory core as shown at 355. If a memory read is required,
then read data is retrieved from the memory core in an operation
shown generally at 357. If the memory access command indicates a
duplex operation (i.e., data flowing both into and out of the
memory core in response to the memory access command), then
execution proceeds to decision block 359. Otherwise, the memory
access command is simplex read command, and the read-data-out
multiplexer is set to select the read-data-in line and thus output
the read data to the host requestor as shown at 361, thereby
completing the simplex operation.
[0051] Continuing with the case of a duplex operation (i.e.,
affirmative determination at block 359), if the atomic command
indicates a binary operation (i.e., it is determined at 363 that
the operation involves a data source other than the retrieved data
value), then the operand is received from a register or external
source (e.g., from an operand register or via the write-data-in
line) at 365 and supplied to the appropriate modify unit.
Thereafter, whether unary operation (negative determination at
decision block 363) or binary operation, the appropriate modify
unit is selected in accordance with the specified atomic operation
and enabled at 367 to generate a modified data value or evaluation
result with respect to the retrieved data and any supplied
operands. The read-data-out multiplexer and write-data-out
multiplexer are set at 369 in accordance with the duplex operation
being performed and any evaluation result, thus enabling concurrent
output of the read data or modified data to the host requestor at
371 and/or storage of operand data (e.g., swap data) or modified
data in the memory core at 373.
[0052] FIG. 6 is a timing diagram illustrating signal timing during
an exemplary duplex operation within the atomic memory device of
FIG. 3. At the start of a core cycle `i,` a memory access command
385 specifying a duplex (atomic) operation is received via the
command/address path 210 (C/A) concurrently with receipt of an
operand 386 to be applied within the duplex operation via the
external data path 212 (D/Q). After a data sampling delay, the
operand is presented on the write-data-in line 232 as shown at 388
and thus to the modify logic of the atomic memory device.
Meanwhile, during the interval marked in FIG. 6 as "Read Data
Retrieval," read data is retrieved from the memory core in
accordance with an address provided in association with the duplex
operation, eventually becoming valid and presented to the modify
logic on the read-data-in line 236 as shown at 390. Assuming a
duplex operation in which read data or modified data (including
swap data) is to be returned to the host requestor, the output of
the modify logic (read data or modified data or swap data, for
example) is output onto the read-data-out line 238 as shown at 392
and, at approximately the same time (or shortly before or after
data output onto rdo line 238), modified data (including swap data)
is output onto the write-data-out line to 234 be written back to
the memory core as shown at 394. Concurrently with write-back to
the memory core, data output onto the read-data-out line is driven
onto the external data path 212 as shown at 396 and thereby
returned to the host requestor during the beginning of the
succeeding core cycle (i.e., core cycle i+1). In the particular
example shown, a simplex memory read operation is commanded at the
start of core cycle i+1 (i.e., as shown at 398), with the data
retrieval operation being carried out with essentially the same
timing as the data retrieval in the preceding duplex operation.
That is, read data i+1 becomes available on the rdi line as shown
at 400 (i.e., after the Read Data Retrieval interval), and is
routed onto the rdo line shortly thereafter as shown at 402. Read
data i+1 is then output onto the external data path as shown at
404, thus completing the simplex memory read just as another read
operation is received in the ensuing core cycle.
[0053] It should be noted that the various circuits disclosed
herein may be described using computer aided design tools and
expressed (or represented), as data and/or instructions embodied in
various computer-readable media, in terms of their behavioral,
register transfer, logic component, transistor, layout geometries,
and/or other characteristics. Formats of files and other objects in
which such circuit expressions may be implemented include, but are
not limited to, formats supporting behavioral languages such as C,
Verilog, and VHDL, formats supporting register level description
languages like RTL, and formats supporting geometry description
languages such as GDSII, GDSIII, GDSIV, CIF, MEBES and any other
suitable formats and languages. Computer-readable media in which
such formatted data and/or instructions may be embodied include,
but are not limited to, computer storage media in various forms
(e.g., optical, magnetic or semiconductor storage media, whether
independently distributed in that manner, or stored "in situ" in an
operating system).
[0054] When received within a computer system via one or more
computer-readable media, such data and/or instruction-based
expressions of the above described circuits may be processed by a
processing entity (e.g., one or more processors) within the
computer system in conjunction with execution of one or more other
computer programs including, without limitation, net-list
generation programs, place and route programs and the like, to
generate a representation or image of a physical manifestation of
such circuits. Such representation or image may thereafter be used
in device fabrication, for example, by enabling generation of one
or more masks that are used to form various components of the
circuits in a device fabrication process.
[0055] In the foregoing description and in the accompanying
drawings, specific terminology and drawing symbols have been set
forth to provide a thorough understanding of the present invention.
In some instances, the terminology and symbols may imply specific
details that are not required to practice the invention. For
example, any of the specific numbers of bits, signal path widths,
signaling or operating frequencies, component circuits or devices
and the like may be different from those described above in
alternative embodiments. In other instances, well-known circuits
and devices are shown in block diagram form to avoid obscuring the
present invention unnecessarily. Additionally, the interconnection
between circuit elements or blocks may be shown as buses or as
single signal lines. Each of the buses may alternatively be a
single signal line, and each of the single signal lines may
alternatively be buses. Signals and signaling paths shown or
described as being single-ended may also be differential, and
vice-versa. A signal driving circuit is said to "output" a signal
to a signal receiving circuit when the signal driving circuit
asserts (or deasserts, if explicitly stated or indicated by
context) the signal on a signal line coupled between the signal
driving and signal receiving circuits. The expression "timing
signal" is used herein to refer to a signal that controls the
timing of one or more actions within an integrated circuit device
and includes clock signals, strobe signals and the like. "Clock
signal" is used herein to refer to a periodic timing signal used to
coordinate actions between circuits on one or more integrated
circuit devices. "Strobe signal" is used herein to refer to a
timing signal that transitions to mark the presence of data at the
input to a device or circuit being strobed and thus that may
exhibit periodicity during a burst data transmission, but otherwise
(except for transition away from a parked condition or other
limited pre-amble or post-amble transition) remains in a
steady-state in the absence of data transmission. The term
"coupled" is used herein to express a direct connection as well as
a connection through one or more intervening circuits or
structures. Integrated circuit device "programming" may include,
for example and without limitation, loading a control value into a
register or other storage circuit within the device in response to
a host instruction and thus controlling an operational aspect of
the device, establishing a device configuration or controlling an
operational aspect of the device through a one-time programming
operation (e.g., blowing fuses within a configuration circuit
during device production), and/or connecting one or more selected
pins or other contact structures of the device to reference voltage
lines (also referred to as strapping) to establish a particular
device configuration or operation aspect of the device. The terms
"exemplary" and "embodiment" are used to express an example, not a
preference or requirement.
[0056] While the invention has been described with reference to
specific embodiments thereof, it will be evident that various
modifications and changes may be made thereto without departing
from the broader spirit and scope. For example, features or aspects
of any of the embodiments may be applied, at least where
practicable, in combination with any other of the embodiments or in
place of counterpart features or aspects thereof. Accordingly, the
specification and drawings are to be regarded in an illustrative
rather than a restrictive sense.
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