U.S. patent application number 09/956748 was filed with the patent office on 2002-04-11 for programmable logic device with hierarchical interconnection resources.
This patent application is currently assigned to Altera Corporation. Invention is credited to Cliff, Richard G., Jefferson, David, Lane, Christopher F., Lee, Andy L., Mejia, Manuel M., Pedersen, Bruce B., Reddy, Srinivas T., Zaveri, Ketan H..
Application Number | 20020041191 09/956748 |
Document ID | / |
Family ID | 27567748 |
Filed Date | 2002-04-11 |
United States Patent
Application |
20020041191 |
Kind Code |
A1 |
Reddy, Srinivas T. ; et
al. |
April 11, 2002 |
Programmable logic device with hierarchical interconnection
resources
Abstract
A programmable logic device has a plurality of super-regions of
programmable logic disposed on the device in a two-dimensional
array of intersecting rows and columns of super-regions. Horizontal
and vertical inter-super-region interconnection conductors are
associated with each row and column, respectively. Each
super-region includes a plurality of regions of programmable logic,
and each region includes a plurality of subregions of programmable
logic. Inter-region interconnection conductors are associated with
each super-region, principally for bringing signals into the
super-region and interconnecting the regions in the super-region.
Local conductors are associated with each region, principally for
bringing signals into the region. At the super-region level the
device may be horizontally and vertically isomorphic, which helps
make it possible to produce devices with low aspect ratios of one
or nearly one. Shared driver circuits may be provided (e.g., for
(1) receiving signals from the subregions and the horizontal and/or
vertical conductors, and (2) applying selected received signals to
the inter-region conductors, the horizontal and vertical
conductors, and possibly also the local conductors). The horizontal
and/or vertical conductors may be axially segmented and buffering
circuitry may be provided for programmably stitching together axial
segments to make longer conductors.
Inventors: |
Reddy, Srinivas T.;
(Fremont, CA) ; Cliff, Richard G.; (Milpitas,
CA) ; Lane, Christopher F.; (Campbell, CA) ;
Zaveri, Ketan H.; (San Jose, CA) ; Mejia, Manuel
M.; (San Jose, CA) ; Jefferson, David; (San
Jose, CA) ; Pedersen, Bruce B.; (San Jose, CA)
; Lee, Andy L.; (San Jose, CA) |
Correspondence
Address: |
FISH & NEAVE
1251 AVENUE OF THE AMERICAS
50TH FLOOR
NEW YORK
NY
10020-1105
US
|
Assignee: |
Altera Corporation
|
Family ID: |
27567748 |
Appl. No.: |
09/956748 |
Filed: |
September 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09956748 |
Sep 19, 2001 |
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09488025 |
Jan 20, 2000 |
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09488025 |
Jan 20, 2000 |
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09363162 |
Jul 28, 1999 |
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09363162 |
Jul 28, 1999 |
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08855192 |
May 13, 1997 |
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09454624 |
Dec 6, 1999 |
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08920298 |
Aug 28, 1997 |
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60028206 |
Oct 10, 1996 |
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60037815 |
Feb 5, 1997 |
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60028207 |
Oct 10, 1996 |
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Current U.S.
Class: |
326/41 |
Current CPC
Class: |
H03K 19/17728 20130101;
H03K 19/17704 20130101; H03K 19/17736 20130101 |
Class at
Publication: |
326/41 |
International
Class: |
H03K 019/177 |
Claims
The invention claimed is:
1. A programmable logic device comprising: a plurality of
super-regions of programmable logic arranged in a two-dimensional
array of rows and columns, each super-region comprising: regions of
programable logic, each region comprising a plurality of subregions
of programmable logic, each subregion programmable to perform a
logic operation on an input signal applied to each subregion; an
inter-region interconnection conductor; at least one region feeding
conductor; a first programmable logic connector configured to
selectively interconnect a region feeding conductor and the
inter-region interconnection conductor; at least one input
conductor wherein: each input conductor is associated with at least
one subregion; each input conductor is selectively interconnected
to a region feeding conductor by a second programmable logic
connector; and each input conductor is configured to convey a
signal from the region feeding conductor to an associated
subregion; a first local feedback conductor associated with each
subregion configured to convey an output signal from each subregion
so that the output signal is available for programmable application
as an input signal to another subregion in the associated region;
and a second local feedback conductor associated with each
subregion configured to convey the output signal to the
inter-region interconnection conductor; a plurality of horizontal
inter-super-region interconnection conductors associated with each
of the rows of super-regions wherein each horizontal
inter-super-region interconnection conductor is programmable to
couple any super-region in the associated row to another
super-region in the associated row; a plurality of vertical
inter-super-region interconnection conductors associated with each
of the columns of super-regions wherein each vertical
inter-super-region interconnection conductor is programmable to
couple any super-region in the associated column to another
super-region in the associated column; and a first plurality of
programmable logic connectors configured to selectively
interconnect the horizontal and vertical inter-super-region
interconnection conductors.
2. The programmable logic device of claim 1 further comprising a
second plurality of programmable logic connectors configured to
selectively apply a signal on the inter-region interconnection
conductors associated with a super-region directly to a subregion
of the super-region as the input signal.
3. The programmable logic device of claim 1 further comprising a
third plurality of programmable logic connectors configured to
selectively apply a signal on the inter-super-region
interconnection conductors to an inter-region interconnection
conductor.
4. The programmable logic device of claim 1 further comprising a
fourth plurality of programmable logic connectors configured to
selectively apply a signal on the inter-super-region
interconnection conductors to a subregion in a super-region as the
input signal.
5. The programmable logic device of claim 1 wherein each subregion
may include a four-input look-up table.
6. The programmable logic device of claim 5 wherein the four-input
look-up table is programmable to provide any logical combination of
four input signals applied to that subregion.
7. The programmable logic device of claim 1 wherein each subregion
may include a register and at least one associated programmable
logic connector for selectively registering the output signal of
the look-up table.
8. The programmable logic device of claim 1 wherein the
inter-region interconnection conductor extends along the regions in
the associated super-region.
9. The programmable logic device of claim 1 wherein the regions are
disposed on either side of the inter-region interconnection
conductor.
Description
[0001] This application claims the benefit of provisional
application No. 60/028,206, filed Oct. 10, 1996, provisional
application No. 60/028,207, filed Oct. 10, 1996, and provisional
application No. 60/037,815, filed Feb. 5, 1997. This is a
continuation of application Ser. No. 09/488,025, filed Jan. 20,
2000, which is a continuation of application Ser. No. 09/363,162,
filed Jul. 28, 1999 (now U.S. Pat. No. 6,181,160), which is a
division of application Ser. No. 08/855,192, filed May 13, 1997
(now U.S. Pat. No. 5,977,793). Application Ser. No. 09/488,025 is
also a continuation of application Ser. No. 09/454,624,filed Dec.
6, 1999, which is a continuation of application Ser. No.
08/920,298, filed Aug. 28, 1997 (now U.S. Pat. No. 5,999,016). All
of application Ser. Nos. 08/855,192, 08/920,298, 09/363,162,
09/454,624, and 09/488,025 are hereby incorporated by reference
herein in their entireties.
BACKGROUND OF THE INVENTION
[0002] This invention relates to programmable logic devices, and
more particularly to programmable logic devices with increased
logic and interconnection capability.
[0003] Programmable logic devices are well known as is shown, for
example, by Pedersen et al. U.S. Pat. No. 5,260,610, Cliff et al.
U.S. Pat. No. 5,260,611, Cliff et al. U.S. Pat. No. 5,689,195, and
Cliff et al. U.S. Pat. No. 5,909,126. All of these references are
hereby incorporated by reference herein in their entirety.
[0004] There is continued interest in programmable logic devices
with greater logic capacity. This calls for devices with larger
numbers of regions of programmable logic. It also calls for logic
devices with more programmable interconnection resources for making
needed connections between the increased numbers of logic regions.
It is important, however, to add interconnection resources
judiciously so that those resources do not begin to take up
excessive amounts of space on the device, thereby unduly
interfering with the amount of additional logic that can be
included in the device. To accomplish this it would be desirable to
find ways to organize programmable logic devices, and especially
the interconnection resources in programmable logic devices, so
that the efficiency of utilization of the interconnection resources
can be greater. In this way more interconnectivity can be provided
in the device to serve more logic in the device without simply
directly scaling up the interconnection resources with the
increased logic capability.
[0005] An example of a possible problem associated with merely
scaling up known programmable logic device architectures is
illustrated by the case of the architecture shown in
above-mentioned Cliff et al. U.S. Pat. No. 5,689,195. In this type
of device regions of programmable logic are disposed on the device
in a plurality of rows of such regions. Each row has an associated
plurality of horizontal interconnection conductors for selectively
conveying signals to, from, and between the regions in that row.
Region-feeding conductors are associated with each region for
selectively bringing signals from the associated horizontal
conductors into the region as input signals. Output signals
produced by each region are selectively applied to the associated
horizontal conductors. Vertical interconnection conductors are
provided for selectively conveying signals between the rows of the
device. Accordingly, a programmable logic device having this type
of architecture basically comprises a row of logic regions and
associated interconnection conductors that has been replicated a
number of times and then provided with vertical interconnection
conductors for interconnecting the rows. To meet the demand for
larger and larger devices it may not be practical to indefinitely
increase the number of regions in a row or the number of rows due
to manufacturing constraints. For example, the aspect ratio of the
device may tend to become too large.
[0006] In view of the foregoing, it is an object of this invention
to provide improved organizations ("architectures") for
programmable logic devices.
[0007] It is a more particular object of this invention to provide
programmable logic device architectures that can efficiently
accommodate larger numbers of programmable logic regions.
[0008] It is another more particular object of this invention to
provide programmable logic device architectures which permit higher
densities of logic regions and which have more uniform horizontal
and vertical characteristics so that there is less preference for
one direction over the other and therefore less tendency toward
designs with high aspect ratios.
SUMMARY OF THE INVENTION
[0009] These and other objects of the invention are accomplished in
accordance with the principles of the invention by providing
programmable logic array integrated circuit devices having a
plurality of super-regions of programmable logic disposed on the
device in a two-dimensional array of intersecting rows and columns
of super-regions. Each super-region includes a plurality of regions
of programmable logic and a plurality of inter-region
interconnection conductors for conveying signals to and between the
regions in that super-region. In some embodiments each super-region
may be somewhat like a short, folded row in the exemplary devices
described in the background section of this specification. For
example, in these embodiments the regions in each super-region may
be disposed along both sides of that super-region's inter-region
interconnection conductors. Thus in these embodiments a
super-region may be viewed as a row of regions that is folded back
along the associated inter-region interconnection conductors. Each
region preferably includes a plurality of subregions of
programmable logic. A typical subregion is programmable to perform
any of several logical operations on a plurality of input signals
applied to the subregion to produce an output signal of the
subregion. Programmable logic connectors are associated with the
regions for selectively bringing signals from the associated
inter-region conductors into the region for use as inputs to the
subregions in that region. Other programmable logic connectors
selectively apply the subregion output signals to the associated
inter-region conductors.
[0010] A plurality of horizontal inter-super-region interconnection
conductors is associated with each row of super-regions for
selectively conveying signals to, from, and between the
super-regions in the associated row. Similarly, a plurality of
vertical inter-super-region interconnection conductors is
associated with each column of super-regions for selectively
conveying signals to, from, and between the super-regions in the
associated column. Programmable logic connectors are provided for
selectively applying signals on the horizontal and vertical
inter-super-region conductors to the inter-region conductors.
Additional programmable logic connectors are provided for
selectively applying subregion output signals to the horizontal and
vertical inter-super-region conductors. And programmable logic
connectors are provided for selectively interconnecting horizontal
and vertical inter-super-region conductors.
[0011] The architectures of this invention can be made more uniform
with respect to the horizontal and vertical axes of the device.
These architectures therefore lend themselves more readily to
square or nearly square layouts. This is desirable because such
layouts have low aspect ratios of one or nearly one. It may also be
possible to achieve greater logic densities with the architectures
of this invention. The inter-super-region interconnection
conductors provide a next level of routing hierarchy (beyond the
routing provided at the region and super-region levels).
Connectivity within the device is increased by segmenting (and
thereby rendering reusable) wiring channels in aligned
super-regions. Any necessary interconnections between super-regions
are then made using inter-super-region conductors.
[0012] Other features that the programmable logic devices of this
invention may have are the provision of two types of horizontal
and/or vertical inter-super-region interconnection conductors.
These are so-called "global" horizontal and/or vertical conductors
that extend along the entire length of the associated row or column
of super-regions, and so-called "half" horizontal and/or vertical
conductors that extend along one of two mutually exclusive halves
of the length of the associated row or column of super-regions. The
mutual exclusivities mentioned in the preceding sentence are
preferred but not absolutely required.
[0013] As a possible addition or alternative to providing separate
global horizontal and half horizontal conductors, two axially
aligned half horizontal conductors can be programmably "stitched"
together to provide a global horizontal conductor when such a
conductor is needed. Thus it may be possible to omit the dedicated
global horizontal conductors. Or it may be preferred to have only
global horizontal conductors and no half horizontal conductors. The
same options exist with respect to the above-described global
vertical and half vertical conductors. The design choices made with
regard to the foregoing options may be influenced by the size of
the device (e.g., the number of logic subregions, regions, and
super-regions on the device).
[0014] If stitching of conductors is provided as mentioned in the
preceding paragraph, it may be provided by programmable buffers
between the conductors being stitched.
[0015] The above-mentioned programmable logic connectors for
selectively bringing signals from the inter-region conductors into
the region may include local conductors that are interleaved
between horizontally adjacent regions. The local conductors may be
of two types: (1) region-feeding conductors for bringing signals
into the adjacent region or regions, and (2) local feedback
conductors for making output signals of the region available as
inputs to the region and possibly also horizontally adjacent
regions. The region-feeding conductors are programmably connectable
to the adjacent inter-region interconnection conductors in order to
receive signals from the inter-region interconnection
conductors.
[0016] The above-mentioned programmable logic connectors for (1)
applying signals on the horizontal and vertical inter-super-region
conductors to the inter-region conductors, (2) applying subregion
output signals to the inter-super-region conductors, and (3)
selectively interconnecting horizontal and vertical
inter-super-region conductors may include drivers which are
effectively shared for these various purposes. For example, one or
more of these drivers may be associated with each logic subregion.
Programmable logic connectors are provided for applying any of
several signals to each driver. For example, these signals may
include (1) one or more output signals of the associated subregion,
(2) one or more global or half vertical conductor signals, and (3)
one or more global or half horizontal conductor signals. The output
signal of each driver may be programmably connected to (1) one or
more global or half horizontal conductors, (2) one or more global
or half vertical conductors, (3) one or more inter-region
interconnection conductors, and (4) one or more local conductors.
These drivers are therefore shared for many purposes such as (1)
driving subregion output signals out onto the global and half
conductors, as well as onto the inter-region interconnection
conductors, (2) making connections between horizontal and vertical
conductors, and (3) driving subregion output signals back onto
local conductors.
[0017] Some of the programmable logic connectors feeding drivers as
described in the preceding paragraph (e.g., those programmable
logic connectors near the periphery of the device) may also receive
signals from input/output ("I/O") pins of the device. This enables
the associated drivers to also be used to drive signals from the
I/O pins to the destinations mentioned above. Some I/O pins may
also have dedicated drivers that programmably feed one or more
global or half conductors and/or one or more inter-region
interconnection conductors.
[0018] Each subregion is fed by multiple inputs. In architectures
with local conductors interleaved between horizontally adjacent
regions, some of these inputs come from the local conductors to the
left of the region that includes that subregion, and some of these
inputs come from the local conductors to the right of the region
that includes that subregion.
[0019] I/O pins along the top, bottom, left, and right sides of the
device may programmably select their output and/or output enable
signals from one or more of the local conductors adjacent the
respective top, bottom, left, or right side of the device.
[0020] From the foregoing it will be apparent that the
region-feeding local conductors are preferably not directly
connected to the global or half conductors. In order to reach a
local line, these global or half conductor signals must first be
routed through the above-mentioned drivers and also in most cases
through inter-region interconnection conductors. This
interconnection architecture reduces the number of programmable
connections used to connect signals to the local lines.
[0021] Some devices may not have dedicated local feedback lines.
This saves programmable interconnect which is wasted if the local
feedback lines are not used. For these devices, the functionality
of the local feedback lines can be achieved by routing signals to
the region-feeding conductors (e.g., via the inter-region
interconnection conductors). If this is done, it may be
advantageous to make some of the inter-region interconnection
conductors span only a very small number of the logic regions,
while other inter-region interconnection conductors span larger
numbers of the logic regions.
[0022] From the foregoing it will be seen that the interconnection
resource architectures of this invention are hierarchical to an
increased degree (e.g., from global or half global to inter-region
to local). Such architectures help to reduce the area required for
a programmable logic device with a given amount of logic capability
by decreasing the total number of programmable interconnections
required. Such architectures also help to increase the speed of the
device by reducing the parasitic loading due to excessive numbers
of programmable interconnections.
[0023] Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a simplified plan view of a portion of an
illustrative embodiment of a programmable logic device constructed
in accordance with the principles of this invention.
[0025] FIG. 2 is a somewhat more detailed, but still simplified,
plan view of an illustrative embodiment of a representative portion
of the FIG. 1 apparatus in accordance with this invention.
[0026] FIG. 3 is an even more detailed, but still simplified plan
view of an illustrative embodiment of a representative portion of
the FIG. 2 apparatus in accordance with this invention.
[0027] FIG. 4 is a more detailed, but still simplified, schematic
block diagram of an illustrative embodiment of a representative
portion of the FIG. 1 apparatus in accordance with this
invention.
[0028] FIG. 5 is a simplified block diagram of representative
portions of another illustrative embodiment of a programmable logic
device constructed in accordance with the invention.
[0029] FIG. 6 is a more detailed, but still simplified, schematic
block diagram of a representative portion of FIG. 5.
[0030] FIG. 7 shows a representative portion of FIG. 6 in still
more detail, but with some modifications in accordance with this
invention.
[0031] FIG. 8 is a schematic block diagram of an illustrative
embodiment of circuitry that may be used in programmable logic
devices in accordance with this invention.
[0032] FIG. 9 is a simplified block diagram showing an illustrative
use of programmable logic devices in accordance with this
invention.
[0033] FIG. 10 is another simplified block diagram showing an
alternative illustrative use of programmable logic devices in
accordance with this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Various aspects of the invention will first be described
with reference to embodiments of the type shown in FIGS. 1-4.
Thereafter, some of these aspects will be further described with
reference to embodiments of the type shown in FIGS. 5-8, which also
show some additional possible aspects of the invention.
Illustrative uses of the programmable logic devices of this
invention are described with reference to FIGS. 9 and 10.
[0035] As shown in FIG. 1, an illustrative embodiment of a
programmable logic array integrated circuit device 10 constructed
in accordance with this invention includes a plurality of
super-regions 20 of programmable logic disposed on the device in a
two-dimensional array of intersecting rows and columns of
super-regions. A plurality of horizontal inter-super-region
interconnection conductors 30 is associated with each of the rows,
and a plurality of vertical inter-super-region interconnection
conductors 40 is associated with each of the columns. The preferred
embodiments of the invention take advantage of recent developments
in semiconductor fabrication, which allow an additional layer of
metal to be provided, by using that additional layer to run
conductors 30 and 40 over super-regions 20. This is one way in
which the present invention can help increase logic density on
device 10. The number of rows and columns (i.e., seven in each
case) shown in FIG. 1 is merely illustrative, and any number of
rows and columns can be provided as desired. Also, although not
shown in FIG. 1, it will be understood that device 10 may
additionally include input and/or output pins for connecting device
10 to external circuitry. Such input and/or output pins
(generically referred to simply as input/output or I/O pins) may be
disposed around the periphery of the device and may be programmably
connectable to various ones of conductors 30 and 40. See also the
techniques used for input/output connections in FIG. 6.
[0036] It will be understood that terms like "row" and "column",
"horizontal" and "vertical", "left" and "right", "upper" and
"lower", and other directional or orientational terms are used
herein only for convenience, and that no fixed or absolute
directions or orientations are intended by the use of these terms.
For example, the words in each of the word pairs mentioned above
can be reversed if desired.
[0037] An illustrative embodiment of a representative super-region
20 is shown in more detail in FIG. 2. In the FIG. 2 embodiment,
super-region 20 includes two rows of regions 50 of programmable
logic disposed on respective opposite sides of a plurality of
horizontal inter-region interconnection conductors 60. For example,
super-region 20 may include eight regions 50 on each side of
conductors 60. This embodiment of super-region 20 is therefore
somewhat like a row of 16 regions 50 that has been folded in half,
back on itself, with the associated interconnection conductors 60
between the two halves of the row.
[0038] An illustrative embodiment of a representative region 50 is
shown in more detail in FIG. 3. In the FIG. 3 embodiment, region 50
includes a plurality of subregions 70 of programmable logic. For
example, region 50 may include eight subregions 70. Each subregion
70 is programmable to perform any of a plurality of logic functions
on input signals 80 applied to the subregion. For example, each
subregion 70 may include a programmable four-input look-up table
for producing a look-up table output which is any logical
combination of the four inputs 80 applied to the subregion. Each
region 70 may additionally include a register and programmable
switches for allowing the look-up table output to be selectively
registered by the register. The output 90 of the subregion may then
be either the registered or unregistered look-up table output. The
outputs 90 of the subregions are selectively applied to
inter-region conductors 60 via programmable logic connectors
("PLCs") 100. Although only one PLC 100 connection to a conductor
60 is shown for each output 90 in FIG. 3, it will be understood
that each output 90 may have such connections to more than one of
conductors 60, if desired. Each output 90 is also fed back within
region 50 so that it can be used as an input to any of the
subregions 70 in that region.
[0039] Each region 50 also includes a plurality of region-feeding
conductors 110 for selectively bringing signals from inter-region
conductors 60 into the region. PLCs 120 programmably connect
conductors 60 to conductors 110 for this purpose. PLCs 120 may be
only partially populated with possible connections (i.e., each of
conductors 110 may be programmably connectable to only a subset of
conductors 60). However, the population densities and distributions
are preferably such that each conductor 60 has several possible
ways into region 50 via conductors 110.
[0040] PLCs 130 allow the signals on conductors 110 and 90 to be
programmably selectively applied to subregion inputs 80. PLCs 130
may be fully populated or partially populated, as desired. Again,
however, if PLCs 130 are only partially populated, the population
densities and distributions are preferably such that each conductor
90 and 110 has a least a couple of ways into each subregion 70 via
conductors 80.
[0041] From the foregoing it will be seen that within a
super-region 20 the regions communicate with one another via the
inter-region conductors 60 of that super-region.
[0042] The illustrative region structure shown in FIG. 3 is
generally like the corresponding portion of the structure shown in
above-mentioned Cliff et al. U.S. Pat. No. 5,689,195 (see
especially FIG. 3 of that patent). However, FIG. 3 is somewhat
simplified as compared to the Cliff et al. FIG. It will be
understood that, if desired, additional features from the Cliff et
al. structure can be included in regions provided in devices of the
present invention. Examples of such possible other features are
additional conductors for so-called fast lines and/or clock
signals, carry and/or cascade interconnections between subregions
70, register control signals derived from local conductors such as
90 and/or 110, etc. The detailed structure of subregions 70 can be
as shown in FIG. 8 of the same Cliff et al. reference.
Alternatively, subregions 70 can be constructed entirely
differently (e.g., as product term logic). Similarly, regions 50
can have a different construction from what is shown in FIG. 3 and
described above. For example, some of the features shown in
McClintock et al. U.S. Pat. No. 5,543,732, McClintock et al. U.S.
Pat. No. 5,614,840, Cliff et al. U.S. Pat. No. 5,541,530, Leong et
al. U.S. Pat. No. 5,592,106, Reddy et al. U.S. Pat. No. 5,694,058,
Pedersen U.S. Pat. No. 5,872,463, and Cliff et al. U.S. Pat. No.
5,909,126 can be employed if desired. These additional references
are also hereby incorporated by reference herein.
[0043] FIG. 4 shows an illustrative embodiment of the
interconnections between a representative super-region 20 and the
horizontal and vertical inter-super-region interconnection
conductors 30 and 40 that are associated with the row and column
that include that super-region. It will be understood that each of
the circuit paths shown in FIG. 4 is only representative of several
similar circuit paths. For example, although only one PLC 100a and
associated structures 90, 150, 152, and 102a are shown in FIG. 4,
multiple groups of such elements are in fact associated with each
super-region 20. The same is true for PLCs 10b, 170, and 210 and
their associated elements.
[0044] Subregion output signals 90 are applied to certain inputs of
PLCs 100a, 10b, 170, and 210. (PLCs 100a and 100b may be subsets of
PLCs 100 in FIG. 3.) Signals from horizontal inter-super-region
conductors 30 can be applied to other inputs of PLCs 100a by PLCs
150 and conductors 152. PLCs 100a select from among the signals
they receive and apply the selected signals to conductors 60 via
drivers 102. In this way signals on horizontal inter-super-region
conductors 30 can be selectively brought into the super-region.
[0045] Signals from vertical inter-super-region conductors 40 can
be applied to other inputs of PLCs 100b by PLCs 180 and conductors
182. PLCs 100b select from among the signals they receive and apply
the selected signals to conductors 60 via drivers 102b. In this way
signals on vertical inter-super-region conductors 40 can be
selectively brought into the super-region.
[0046] Signals from horizontal inter-super-region conductors 30 can
be applied to other inputs of PLCs 170 by PLCs 160 and conductors
162. PLCs 170 can select these horizontal inter-super-region
conductor signals or subregion output signals 90 for application to
vertical inter-super-region conductors 40 via drivers 172. Elements
160, 170, and 172 therefore allow signals on horizontal conductors
30 to be applied to vertical conductors 40. Elements 170 and 172
additionally allow subregion outputs 90 to be applied to vertical
conductors 40.
[0047] Signals from vertical inter-super-region conductors 40 can
be applied to other inputs of PLCs 210 by PLCs 200 and conductors
202. PLCs 210 can select these horizontal inter-super-region
conductor signals or subregion output signals 90 for application to
horizontal inter-super-region conductors 30 via drivers 212.
Elements 200, 210, and 212 therefore allow signals on vertical
conductors 40 to be applied to horizontal conductors 30. Elements
210 and 212 additionally allow subregion outputs 90 to be applied
to horizontal conductors 30.
[0048] FIG. 4 also shows PLCs 120 and drivers 122 for selectively
driving signals on region interconnection conductors 60 into the
regions of the super-region (as in FIG. 3).
[0049] As described above for PLCs 120, PLCs 150, 160, 180, and 200
may have full or partial populations of programmable connections
from their respective input conductors 30 and 40 to their
respective output conductors 152, 162, 182, and 202. If partial
populations are used, the densities and distributions of the
programmable connections are preferably such that each input
conductor 30 or 40 has several ways to get to PLCs 100a, 100b, 170,
and 210.
[0050] Drivers 102a, 102b, 172, and 212 are preferably programmably
controlled tri-state drivers so that more than one such driver can
be connected to a conductor 30, 40, or 60. only one of the drivers
connected to a conductor will typically be active; the other
drivers will be tri-stated. Alternatively, all of the drivers 172
and 212 connected to a conductor 30 or 40 may be tri-stated, and
the conductor may be used for another purpose (e.g., bringing a
signal into the device from an input/output pin of the device).
[0051] The output signals of drivers 102a, 102b, 172, and 212 are
shown in FIG. 4 as having fixed (i.e., non-programmable)
connections to conductors 30, 40, and 60. This implies that each
driver 102a, 102b, 172, and 212 has a fixed output connection to
one particular conductor 30, 40, and 60. It will be understood,
however, that as an alternative to this construction each driver
102a, 102b, 172, and/or 212 could have programmable connections to
one or more of the associated conductors 30, 40, and 60.
[0052] The subregion output signals 90 shown in FIG. 4 can come
directly from particular subregion outputs 90 shown in FIG. 3.
Alternatively, there may be programmable switching between the
subregion outputs 90 shown in FIG. 3 and the inputs 90 shown in
FIG. 4 so that each input 90 in FIG. 4 can be selected from among
several outputs 90 of the type shown in FIG. 3.
[0053] From the foregoing it will be seen that devices of this
invention can be constructed with no significant preferences for
communication via horizontal conductors 30 as opposed to vertical
conductors 40 or vice versa. For example, there can be the same
number of horizontal conductors 30 for each row as there are
vertical conductors 40 for each column. There can be the same
number of routes of each kind via PLCs 102a as there are via PLCs
102b. There can be the same number of routes of each kind via PLCs
172 as there are via PLCs 210. There is therefore no preference for
communication either horizontally or vertically, and if the device
is made with approximately the same number of rows and columns, it
can be substantially the same in either direction at the level of
communication between the super-regions. Devices of this invention
can accordingly have the advantage that they are not merely rows of
programmable logic that are repeated to make two-dimensional
arrays. Rather, they can be truly isomorphic in both directions for
purposes of inter-super-region communication. And with the same or
approximately the same numbers of rows and columns, devices of this
invention can have advantageously low aspect ratios of one or
nearly one.
[0054] The alternative illustrative programmable logic integrated
circuit device 510 shown in FIG. 5 includes several rows and
several columns of super-regions 520 of programmable logic. For
example, there may be 20 rows and ten columns of super-regions 520
on device 510.
[0055] Each super-region 520 includes several regions 530 of
programmable logic. For example, each super-region 520 may include
eight regions 530.
[0056] Each region 530 includes several subregions 540 of
programmable logic. For example, each region 530 may include ten
subregions 540. To avoid undue clutter in FIG. 5, the subregions
540 are shown individually in only the extreme upper left-hand
region 530.
[0057] Each subregion 540 is typically programmable to perform any
of several relatively elementary logic operations on input signals
applied to that subregion. For example, each subregion 540 may
include a four-input look-up table which is programmable to provide
any logical combination of four input signals applied to that
subregion. Each subregion 540 may also include a register and
associated PLCs for selectively registering the output signal of
the look-up table.
[0058] A plurality of horizontal inter-super-region interconnection
conductors 550 is associated with each row of super-regions 520.
Each group of conductors 550 may include global horizontal
conductors (which extend along the entire length of the associated
row of super-regions 520) and half horizontal conductors (which
extend along respective left or right halves of the associated row
of super-regions 520). Axially aligned half horizontal conductors
550 may be programmably interconnected by PLCs 552 to effectively
make a global horizontal conductor 550. Depending on such factors
as the size of device 510, dedicated global horizontal conductors
may be omitted and sole reliance placed on interconnecting axially
aligned half horizontal conductors 550 when a global horizontal
conductor is needed. As another alternative, all of conductors 550
may be global and the half horizontal conductors may be
omitted.
[0059] A plurality of vertical inter-super-region interconnection
conductors 560 is associated with each column of super-regions 520.
Like each group of horizontal conductors 550, each group of
vertical conductors 560 may include global vertical conductors
(extending along the entire length of the associated column), or
half vertical conductors (extending along respective top or bottom
halves of the associated column), or both global and half vertical
conductors. Axially aligned half vertical conductors 560 may be
programmably interconnected by PLCs 562 between those conductors.
Although FIG. 5 shows the vertical conductors 560 associated with
each column of super-regions 520 collected together in a single
group, it may be preferable to distribute the vertical conductors
570 for each column among the regions 530 in that column as shown
in FIG. 6.
[0060] Each super-region 520 has an associated plurality of
inter-region interconnection conductors 570 that extend along the
regions 530 in that super-region. Conductors 570 are frequently
referred to below as "fractional horizontal" or simply "fractional"
conductors.
[0061] A representative portion of device 510 is shown in more
detail in FIG. 6. In particular, FIG. 6 shows the lower right-hand
corner of device 510. The greatest amount of detail is shown toward
the right in FIG. 6. Some of that detail is omitted toward the
left. FIG. 6 shows that regions 530 are interspersed with local
conductors 580. These are of two types: (1) region-feeding
conductors 580a and (2) local feedback conductors 580b. The
region-feeding conductors 580a on each side of each region 530 are
programmably connectable by PLCs 572 to the fractional conductors
570 associated with the super-region 520 that includes that region
in order to bring signals from the fractional conductors 570 into
the adjacent regions. Each subregion 540 has several main input
conductors 590, some of which come from the left and some of which
come from the right. For example, each subregion 540 may have four
input conductors 590, two from the left and two from the right.
Each of conductors 590 is programmably connectable by PLCs 582 to
the local conductors 580 to the left or right of the associated
subregion 540, depending on the direction from which that conductor
590 comes to the subregion.
[0062] Each subregion 540 has at least one main output conductor
600. (In connection with less crowded FIG. 7 it will be explained
that each subregion 540 preferably has more than one output. But
for present purposes it will suffice to show and describe one
representative main output conductor 600.) At least one PLC 610 is
associated with each subregion output conductor 600. The signal on
the subregion output conductor 600 is applied to one input terminal
of the associated PLC 610. Other inputs to each PLC 610 are (1)
signals from several adjacent global horizontal and half horizontal
conductors 550 (brought into the associated region via lateral
conductors 552), and (2) signals from several adjacent global
vertical and half vertical conductors 560. PLCs 610 that are
adjacent to horizontal or vertical I/O pins 630 and/or 640 may also
have as inputs signals from those I/O pins. In the simplest case
each PLC 610 is programmable to select one of its inputs as its
output. The output of each PLC 610 is applied to an associated
driver 620.
[0063] The output of each driver 620 can be applied to (1) one or
more adjacent global or half horizontal conductors 550 (via PLCs
622), (2) one or more adjacent fractional horizontal conductors 570
(via PLCs 624), (3) one or more adjacent global or half vertical
conductors 560 (via PLCs 626), (4) one or more adjacent
region-feeding conductors 580a (via PLCs 628), and/or (5) local
feedback conductors 580b.
[0064] From the foregoing it will be seen that in addition to
providing the paths by which subregion output signals 600 are
driven out to conductors 550, 560, 570, and 580, PLCs 610 and
drivers 620 provide the paths by which conductors 550 and 560 can
be interconnected, and the paths by which signals on conductors 550
and 560 are brought into the super-regions 520. For the most part
this last-mentioned routing involves communication to the
fractional horizontal conductors 570 of each super-region and from
the fractional horizontal conductors to the region-feeding
conductors 580a of each region (although it may occasionally be
possible to route a signal from a conductor 550 or 560 more
directly to a region 530 via the local conductors 580 of that
region without making use of the adjacent conductors 570). This
method of routing reduces the number of programmable connections
used to connect signals to region-feeding conductors 580a. In
effect, conductors 550 and 560 provide communication between
super-regions 520, while the conductors 570 associated with each
super-region provide most of the communication between the regions
530 in that super-region. Local conductors 580 (especially local
feedback conductors 580b) provide most of the communication between
the subregions 540 adjacent to those conductors 580.
[0065] It will be noted that interleaving local conductors 580
between horizontally adjacent regions 530 provides additional local
signal routing between the subregions 540 in horizontally adjacent
regions 530. For example, the output signal 600 of a subregion 540
in the middle region 530 shown in FIG. 6 can be applied as an input
to a subregion 540 in the right-hand region 530 using only a local
conductor 580 and without the need to use a fractional horizontal
conductor 570.
[0066] Local conductors 580 adjacent the edges of device 510 are
used as the sources for the output data and output enable signals
of I/O pins 630 and 640. PLCs 584 select the output data signals,
and PLCs 586 select the output enable signals. Each output data
signal is applied to the data input terminal of an associated
tri-state driver 650, and each output enable signal is applied to
the control input terminal of an associated tri-state driver
650.
[0067] FIG. 6 shows that some of I/O pins 630 and 640 may have
dedicated drivers 632a, 632b, 642 that programmably feed one or
more conductors 550, 570, and 560 via PLCs 634a, 634b, and 644,
respectively.
[0068] FIG. 7 shows a representative portion of FIG. 6 in still
more detail. However, FIG. 7 also shows that some of the
interconnection resources that are included in FIG. 6 can be
omitted and their functions performed by other interconnection
resources as will now be explained.
[0069] FIG. 7 shows that each subregion 540 may have more than one
main output 600. For example, each of PLCs 610 in FIG. 7 is shown
as receiving both the registered and combinatorial output signals
of the associated subregion 540, and there are two such PLCs 610
associated with each subregion. The other inputs to each PLC 610
are as described above in connection with FIG. 6. Although FIGS. 6
and 7 show each PLC 610 receiving inputs 600 from only one
subregion 540, this is not necessarily the case, and each PLC 610
could instead receive inputs 600 from two or more subregions 540 if
desired.
[0070] In the embodiment shown in FIG. 7 drivers 620 drive only to
conductors 550 (via PLCs 622), conductors 560 (via PLCs 626), and
conductors 570 (via PLCs 624). Drivers 620 do not have direct
connections to region-feeding conductors 580a, and local feedback
conductors 580b are entirely omitted. Conductors 580a therefore
serve for both region-feeding and local feedback. Moreover all
region-feeding and local feedback signals must also pass through
fractional horizontal conductors 570. Because of the greater number
of uses to which conductors 570 are put in this embodiment, it may
be desirable to axially segment some of conductors 570. Each axial
segment of such a conductor 570 would extend to only a small number
of regions 530 (e.g., one or two regions 530), while the
unsegmented conductors 570 would extend to all the regions 530 in
the associated super-region 520. Eliminating dedicated local
feedback conductors 580b as shown in FIG. 7 saves substantial
amounts of local interconnect when local feedback is not
needed.
[0071] FIG. 7 also shows that in addition to main outputs 600, each
subregion 540 may have one or more direct connections 700 to
adjacent subregions. For example, one of direct connections 700 may
be usable for an arithmetic carry out signal from one subregion to
another. Another of direct connections 700 may be usable for a
cascade connection from one subregion to another. Above-mentioned
Cliff et al. U.S. Pat. No. 5,689,195 is exemplary of how carry and
cascade connections may be provided and used in programmable logic
devices.
[0072] A typical device may include 20 rows of super-regions 520,
with each row having 80 regions 530. Each region 530 may have ten
subregions 540. Each row may have 480 half horizontal conductors
550 for each half of the row. The device may have a total of 6400
half vertical conductors 560 (40 for each half of each column of
regions 530). A device of this size may not need global horizontal
or global vertical conductors. Each super-region 520 may be spanned
by 120 fractional horizontal conductors 570. Each of these
conductors may be programmably connected to two of the
region-feeding conductors 580a in each group of conductors 580a
that it spans. Each group of local lines 580 may include 24
region-feeding conductors 580a and ten local feedback conductors
580b. There may be two drivers 620 per subregion 540. Each of
drivers 620 may feed two half horizontal conductors 550, three
fractional horizontal conductors 570, and one half vertical
conductor 560. Each PLC 610 may be fed by two half vertical
conductors 560, six half horizontal conductors 550, and two
subregion outputs 600. As has been mentioned in connection with
FIG. 6, some of PLCs 610 may also be fed by an I/O pin 630 and/or
640, with each I/O pin typically feeding four different PLCs 610. A
typical device 510 may have 480 I/O pins 630 and 640.
[0073] It will be understood that the foregoing device size,
numbers of interconnection conductors, numbers of PLCs, etc., are
only illustrative, and that other sizes and numbers can be used if
desired.
[0074] FIG. 8 shows an illustrative embodiment of a preferred
bi-directional buffering circuit 552/562 in accordance with this
invention. As the reference number 552/562 suggests, this circuit
can be used for programmably connecting two half horizontal
conductors 550 as shown at 552 in FIG. 5, or for programmably
connecting two vertical conductors 560 as shown at 562 in FIG.
5.
[0075] Programmable function control element ("FCE") 810 controls
the direction of buffering (i.e., whether from the left-hand
conductor 550 or 560 to the right-hand conductor 550 or 560 or vice
versa). FCE 820 controls segmentation (i.e., whether or not the
left-and right-hand conductors 550 and 560 are connected to one
another). If FCE 810 is programmed logic 0 and FCE 820 is
programmed logic 1, the output of NOR gate 830 is logic 0 and all
of transistors 840 and 850 are off, thereby disconnecting the left-
and right-hand segments of conductor 550 or 560 from one another.
On the other hand, if both of FCEs 810 and 820 are programmed logic
0, then the output of NOR gate 830 is logic 1 and both of
transistors 840 are off while both of transistors 850 are on. This
allows the signal on left-hand conductor segment 550 or 560 to flow
through transistor 850b, to be amplified by serially connected
inverting drivers 860 and 880, and to then be applied to the
right-hand conductor segment 550 or 560 via transistor 850a.
Inverter 870 is a small level-corrector for the circuit. Various
forms of the word "amplify" are sometimes used herein and in the
appended claims to refer to the signal strengthening and
restoration that is performed by buffering circuit elements such as
860 and 880.
[0076] If FCE 810 is programmed logic 1 and FCE 820 is programmed
logic 0, the output of NOR gate 830 is logic 0 and transistors 840
are on while transistors 850 are off. This allows the signal on
right-hand conductor segment 550 or 560 to flow through transistor
840b, to be amplified by drivers 860 and 880, and to be applied to
the left-hand conductor segment 550 or 560 via transistor 840a.
[0077] Programming both of FCEs 810 and 820 logic 1 produces the
same condition as programming FCE 810 logic 1 and programming FCE
820 logic 0.
[0078] From the foregoing, it will be seen that circuit 552/562 is
programmable to either (1) electrically isolate the left- and
right-hand conductor segments 550 or 560 from one another, (2)
cause the left-hand conductor segment 550 or 560 to drive the
right-hand segment via buffering circuit elements 860 and 880, or
(3) cause the right-hand conductor segment 550 or 560 to drive the
left-hand segment via the buffering circuit elements.
[0079] Among the advantages of using programmable segmentation
buffer circuitry of the type shown in FIG. 8 is that cutting off an
unused conductor segment conserves power that would otherwise be
wasted to drive the entire line. Such circuitry also facilitates
scaling of programmable logic device architectures by providing a
way of buffering long interconnection conductors. Segmentation and
buffering reduces the load seen by the drivers (such as 620)
driving the segmented and buffered conductors. This allows driver
size and power to be reduced. Segmentation and buffering also
improves timing for both corner-to-corner and same quadrant paths,
and it improves fitting of logic into programmable logic devices by
segmenting global conductors. Circuit 552/562 can be used for
segmentation and buffering of conductors of any kind and length,
not just the half horizontal and half vertical conductors that are
specifically mentioned above.
[0080] Those skilled in the art will appreciate that the
programmable logic devices of this invention have many possible
uses. For example, FIG. 9 illustrates use of a programmable logic
device 1002 of this invention in a digital processing system 1000
including other digital components such as processing unit 1004,
memory 1006, input device or circuitry 1008, and output device or
circuitry 1010. System 1000 may be any computer or computer-like
system with the addition of programmable logic device 1002 to
perform any desired functions of or for the system. For example,
programmable logic device 1002 may be programmed from memory 1006
under the control of processing unit 1004. Thereafter, programmable
logic device 1002 may operate under the control of processing unit
1004 on data or other signals supplied from processing unit 1004,
memory 1006, and/or input 1008 in order to produce output data or
other signals that are applied to processing unit 1004, memory
1006, and/or output 1010. Processing unit 1004 may be a
general-purpose processor (e.g., a microprocessor), as is typical
if processor 1004 is the processor of a general-purpose computer
system that includes programmable logic device 1002. Alternatively,
processing unit 1004 may be any special-purpose circuitry for
performing or controlling any particular functions or tasks. The
various components and interconnections shown in FIG. 5 are only
illustrative. Various ones of these components and interconnections
can be omitted if desired. Similarly, additional components and
interconnections can be included if desired. For example, input
1008 and output 1010 could be combined into one input/output device
or circuit. Any suitable technologies can be used for any of
components 1004, 1006, 1008, and 1010.
[0081] FIG. 10 shows that the programmable logic devices of this
invention (e.g., device 1002) can be mounted on a printed circuit
board 1020, possibly with other circuitry (e.g., of the various
types shown in FIG. 9). In a printed circuit board implementation
of FIG. 9 type circuitry, input device or circuitry 1008 from FIG.
9 is likely to be embodied as input interface circuitry 1008' for
use in making connections to external input devices and/or circuits
(not shown). Similarly, output device or circuitry 1010 from FIG. 9
is likely to be embodied as output interface circuitry 1010' for
use in making connections to external output devices and/or
circuits (not shown). In other respects the components and
connections shown in FIG. 10 may be similar to the corresponding
components and connections shown in FIG. 9. Again, various
components and connections shown in FIG. 10 can be omitted from
circuit board 1020 if desired, and/or other components and
connections can be added to that board.
[0082] Various technologies can be used to implement programmable
logic devices employing the super-regions, regions, and subregions
of this invention, as well as the various components of those
super-regions, regions, and subregions (e.g., the PLCs and the
programmable function control elements ("FCEs") which control the
PLCs). For example, each PLC can be a relatively simple
programmable connector such as a switch or a plurality of switches
for connecting any one of several inputs to an output.
Alternatively, each PLC can be a somewhat more complex element
which is capable of performing logic (e.g., by logically combining
several of its inputs) as well as making a connection. In the
latter case, for example, each PLC can be product term logic,
implementing functions such as AND, NAND, OR, or NOR. Examples of
components suitable for implementing PLCs are EPROMs, EEPROMs, pass
transistors, transmission gates, antifuses, laser fuses, metal
optional links, etc. As has been mentioned, the components of PLCs
can be controlled by various, programmable, function control
elements ("FCEs"). (With certain PLC implementations (e.g., fuses
and metal optional links) separate FCE devices are not required.)
FCEs can also be implemented in any of several different ways. For
example, FCEs can be SRAMs, DRAMs, first-in first-out ("FIFO")
memories, EPROMs, EEPROMs, function control registers (e.g., as in
Wahlstrom U.S. Pat. No. 3,473,160), ferro-electric memories, fuses,
antifuses, or the like. From the various examples mentioned above
it will be seen that this invention is applicable to both
one-time-only programmable and reprogrammable devices.
[0083] It will be understood that the foregoing is only
illustrative of the principles of this invention and that various
modifications can be made by those skilled in the art without
departing from the scope and spirit of the invention. For example,
the number of rows and columns of super-regions can be varied.
Similarly, the number of regions in each super-region can be
varied, as can the number of subregions in each region. The numbers
of the various types of interconnection resources such as PLCs 100,
120, 150, 160, 170, 180, 200, 210, 572, 582, 610, 622, 624, and
626, drivers 102, 172, 212, and 620, etc., can all be varied as
desired. Various types of programmable logic can be used in the
subregions, and various technologies can be used for the PLCs and
other elements of the device, all as suggested above.
* * * * *