U.S. patent number RE36,789 [Application Number 08/690,462] was granted by the patent office on 2000-07-25 for switchable active termination for scsi peripheral devices.
This patent grant is currently assigned to La Cie, Limited. Invention is credited to Paul G. Mandel, Richard A. Ralston, Jr., Gary E. Robertson.
United States Patent |
RE36,789 |
Mandel , et al. |
July 25, 2000 |
Switchable active termination for SCSI peripheral devices
Abstract
A switchable active termination device internally mounted within
a peripheral device and electrically connected to the end of a
Small Computer Systems Interface (SCSI) bus cable. Through use of a
pair of SCSI active terminator circuit chips, the termination
device actively terminates the data lines of the bus cable in a
first operating mode in response to a first digital command by
providing precise resistive pull-up to a predetermined value on
each data line. In a second mode of operation responsive to a
second digital command, the termination device disconnects all
terminating resistors. Activation of the termination modes is
logically driven from an included switch, with visual indication of
the presence of an active termination state provided by a light
emitting diode.
Inventors: |
Mandel; Paul G. (Kansas City,
MO), Ralston, Jr.; Richard A. (Shawnee Mission, KS),
Robertson; Gary E. (North Kansas City, MO) |
Assignee: |
La Cie, Limited (Hillsboro,
OR)
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Family
ID: |
22470612 |
Appl.
No.: |
08/690,462 |
Filed: |
July 29, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
135967 |
Oct 14, 1993 |
05422580 |
Jun 6, 1995 |
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Current U.S.
Class: |
326/30; 326/86;
326/90; 375/257 |
Current CPC
Class: |
H04L
25/0298 (20130101); G06F 13/4086 (20130101) |
Current International
Class: |
H03K
17/16 (20060101); H03K 017/16 () |
Field of
Search: |
;326/30,86,90
;375/257 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0531630A1 |
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Mar 1993 |
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EP |
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4142081A1 |
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Dec 1991 |
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DE |
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2254227A |
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Sep 1992 |
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GB |
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2286953A |
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Aug 1995 |
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GB |
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WO 94/08305 |
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Apr 1994 |
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WO |
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Other References
SCSI Active Terminator, by Unitrode Integrated Circuits
Corporation, Apr. 1992. .
SCSI and Active Termination Application Note, Third Draft, by Paul
D. Aloisi of UICC. Jun. 1993. .
SCSI Bus Terminators, Product Bulletin, Motorola Corporation, Jul.
1992. .
Article from MacWEEK, ProductWatch, "Hey, you get off of my
platform!", La Cie Ltd., Apr. 17, 1990. .
CIRRUS 5000 drawings, La Cie Ltd. .
"Choosing Proper Terminators for the SCSI-Bus System Environment,"
Electronic Design, Mar. 18, 1993. .
IBM Technical Disclosure Bulletin, vol. 24, No. 8, Jan. 1982. .
Product & Applications Handbook 1993-1994, by Unitrode
Integrated Circuits Corporation (U.I.C.C.), Jun. 1993. .
Unitrode, SCSI Active Terminator, UC5601, data manual, Sep. 9,
1991..
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Primary Examiner: Tokar; Michael J.
Assistant Examiner: Roseen; Richard
Attorney, Agent or Firm: Stoel Rives LLP
Claims
We claim:
1. A SCSI termination device, comprising:
a first bus connector for connecting the termination device with a
first SCSI bus cable;
a second bus connector for connecting the termination device to a
SCSI peripheral device;
a third bus connector for connecting the termination device with a
second SCSI bus cable;
circuit means .Iadd.comprising a pair of active terminator circuit
chips .Iaddend.connected via a connection bus to the first, second
and third bus connectors for selectively providing termination of
the SCSI bus cables connected to the first and third bus
connectors; and
switch means for selecting activation of the .[.circuit means.].
.Iadd.active terminator circuit chips .Iaddend.to terminate the
SCSI bus cables.
2. The SCSI termination device as in claim 1 wherein the
.Iadd.first .Iaddend.SCSI bus cable further includes a power supply
line and a ground line, the circuit means including means for
connecting to the power supply and ground lines.
3. The SCSI termination device as in claim 1 wherein the peripheral
device comprises a storage device.
4. The SCSI termination device as in claim 1 further including a
light emitting diode responsive to the switch means for providing
an indication of the activation of the circuit means. .[.5. The
SCSI termination device as in claim 1 wherein the circuit means
comprises a pair of active
terminator circuit chips..].6. The SCSI termination device as in
claim .[.5.]. .Iadd.1 .Iaddend.wherein the active terminator
circuit chips
comprise UC5603 chips. 7. The SCSI termination device as in claim 1
further including: means for connecting the circuit means to a
power
supply provided for operation of the SCSI peripheral device. 8. The
SCSI termination device as in claim 7 wherein the termination
device is
installed within the SCSI peripheral device. 9. The SCSI
termination device as in claim 7 further including means for
filtering transients from the power supplied from the power supply
provided for operation of the
SCSI peripheral device. 10. The SCSI termination device as in claim
1 wherein the SCSI .Iadd.peripheral device comprises a
.Iaddend.peripheral storage device, the termination device further
including jumper means associated with the connection bus for
enabling reset of the peripheral
storage device. 11. The SCSI termination device as in claim 10
wherein the peripheral storage device comprises a disk drive and
the jumper means
facilitates a disk drive reset operation. 12. A SCSI termination
device, comprising:
a first bus connector for connecting the termination device with a
SCSI bus cable terminating at a SCSI peripheral storage device;
circuit means connected via a connection bus to the first bus
connector for selectively providing termination of the SCSI bus
cable;
switch means for selecting activation of the circuit means to
terminate the SCSI bus cable; and
jumper means associated with the connection bus for enabling a
reset of the
peripheral storage device. 13. The SCSI termination device as in
claim 12 wherein the peripheral storage device comprises a disk
drive and the
jumper means facilitates a disk drive reset operation. 14. The SCSI
termination device as in claim 12 further including a light
emitting diode responsive to the switch means for providing an
indication of the activation of the circuit means and the
termination of the SCSI bus cable.
5. A SCSI termination device, comprising:
a first connector for connecting to a SCSI cable;
a second connector for connecting to a SCSI peripheral device;
a bus connecting the first connector to the second connector;
circuit means connected to the bus for selectively providing
termination of the SCSI cable connected to the first connector;
means coupled to the circuit means for selecting activation of the
circuit means; and
a jumper between the first and second connectors for enabling a
reset of
the SCSI peripheral device. 16. The SCSI termination device as in
claim 15 wherein the peripheral device comprises a disk drive and
the jumper
facilitates a disk drive reset operation. 17. The SCSI termination
device as in claim 15 further including a light emitting diode for
providing an indication of the termination of the SCSI bus cable.
Description
TECHNICAL FIELD
The present invention relates to line termination devices and, in
particular, to a switchable active termination device for
connection to the end of a Small Computer Systems Interface (SCSI)
bus cable.
SUMMARY OF THE INVENTION
There is a known need for some sort of termination at the ends of
Small Computer Systems Interface (SCSI) bus cables that are coupled
to peripheral devices. The present invention comprises a switchable
active termination device utilizing a pair of commercially produced
SCSI active terminator circuit chips installed within a peripheral
device and connected in parallel to the SCSI bus cable which is
connected to the host peripheral device. Power for the active
terminator circuit chips is provided through one line of the bus
cable or from the peripheral device power supply. Activation of the
termination function that is provided by the included terminator
circuit chips is logically driven from a user activated switch,
with visual indication of the presence of an active termination
state provided by a light emitting diode.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present invention may be had
by reference to the following Detailed Description when taken in
conjunction with the accompanying Drawings wherein:
FIG. 1 illustrates the installation of the switchable active
termination device of the present invention within a peripheral
device and connected to an SCSI bus cable; and
FIG. 2 shows a schematic circuit diagram of the switchable active
termination device of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to FIG. 1, there is illustrated the installation of a
switchable active termination device 10 according to the present
invention within the housing 12 for a conventional SCSI peripheral
device 14 such as a peripheral storage device or the like. Unlike
known prior art termination devices, the termination device 10 of
the present invention is internally mounted within the housing 12
of the peripheral device 14 thus facilitating space savings, ease
of operation and bus cable connection.
The termination device 10 includes a connector bus 16 for
connecting at least one header 18 to the peripheral device 14 and
at least one header 20 for connecting to at least one conventional
SCSI bus cable 22. The header 20 allows for the connection to two
SCSI bus cables (as shown) to accommodate computer system designs
wherein the peripheral device 14 is not located at the distal end
of a bus cable.
The termination device 10 is powered from the power supply 24
provided within the housing 12 for the peripheral device 14, and is
also powered, as will be discussed in more detail below, from the
power line included in the SCSI bus cable 22 (and connector bus
16). Power from supply 24 is transmitted to the termination device
10 along line 26 and to the peripheral device 14 along line 28. The
termination device 10 further includes a switch 30 for controlling
device operation having an unactuated position (shown) and an
actuated position (not shown). A light emitting diode 32 is also
included and is responsive to the activation of the switch 30 to
provide a visual indication to the user of the present active
termination state for the termination device 10.
Reference is now made to FIG. 2 wherein there is shown a schematic
circuit diagram of the switchable active termination device 10 of
the present invention comprising two SCSI active terminator circuit
chips 34a and 34b connected in parallel to the connector bus 16.
Circuit chips 34a and 34b preferably each comprise a UC5603 9-line
SCSI Active Terminator chip manufactured by Unitrode Integrated
Circuits. A single UC5601 18-line SCSI Active Terminator Chip
(Unitrode) may be substituted for the foregoing two UC5603 chips if
desired. SCSI data lines one through nine, see reference 36, of the
SCSI bus cable 22 (and connector bus 16) are connected to the
termination interface port 38 of the first circuit chip 34a.
Similarly, SCSI data lines ten through eighteen, see reference 40,
of the SCSI bus cable 22 (and connector bus 16) are connected to
the termination interface port 38 of the second circuit chip
34b.
The termination power supply line 42 of the SCSI bus cable 22 (and
connector bus 16) is connected to the power input (PWR) of both
circuit chips 34a and 34b. Similarly, the ground line 44 of the
SCSI bus cable 22 (and connector 16) is connected to the ground
input (GND) of both circuit chips 34a and 34b. As discussed above,
the termination circuit 10 also receives power from the power
supply 24 for the peripheral device 14 along line 26 comprised of a
power line 46 (including a flow diode 48) connected to the supply
line 42 and a ground line 50 connected to the ground line 44. A
capacitor 52 connected between the power line 46 and ground line 44
filters transients present in the power supplied to the termination
device 10 from the power supply 24 for the peripheral device 14.
The power supply line 42 is further connected through LED 32 to the
disconnect ports (DIS) of both circuit chips 34a and 34b, with a
connection further made from the disconnect ports to the ground
line 44 through actuation switch 30. The termination device further
includes a pair of capacitors 54 connected from the regulator
output port (REG) of each circuit chip 34a and 34b to the ground
line 44.
When the switch 30 is placed in the unactuated position (as shown),
the disconnect ports (DIS) are applied with power (logic high) from
supply line 42 and the circuit chips 34a and 34b respond by
providing a precision resistive pull-up to a predetermined
reference voltage on all data lines one through eighteen, see
references 36 and 40, of the bus cable 22. When the switch 30 is
placed in the actuated position (not shown), the disconnect ports
(DIS) of circuit chips 34a and 34b are grounded (logic low), and
current flows through and illuminates LED 32. In response to the
grounding of the disconnect ports (DIS), the terminating resistors
within the circuit chips 34a and 34b connected to the data lines
one through eighteen, see references 36 and 40, of the SCSI bus
cable 22 (and connector bus 16) are disconnected.
The terminating resistors selectively connected to each data line
of the SCSI bus cable 22 (and connector bus 16) provide a matched
impedance to the impedance of the bus cable 22. Such impedance
matching allows for fewer SCSI retries and increased bus speed
(bandwidth) for data communication to and from the peripheral
device 14. Furthermore, the present termination device facilitates
a line frequency response time that substantially exceeds the
performance of prior art external termination devices, while
reducing pulse fluctuations and noise on the data lines (36 and 40)
of the bus cable 22. The termination device 10 further includes a
jumper (as generally indicated at 56) for providing an electrical
connection between pin forty (-RST) of standard SCSI header 20 at
the SCSI bus cable 22 and pin forty (-RST) of standard SCSI header
18 at the peripheral device 14. The jumper 56 enables a reset
operation to be performed on the SCSI peripheral device, and is
especially useful when the peripheral device is a storage device
such as a disk drive.
Although a preferred embodiment of the switchable active
termination device of the present invention has been illustrated in
the accompanying Drawings and described in the foregoing Detailed
Description, it will be understood that the invention is not
limited to the embodiment disclosed, but may be modified without
departing from the spirit of the invention as set forth and defined
by the following claims.
* * * * *