TI SN74BCT8373

SCBS471 − JUNE 1990 − REVISED JUNE 1994
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Member of the Texas Instruments SCOPE 
Family of Testability Products
Octal Test-Integrated Circuit
Functionally Equivalent to SN74F373 and
SN74BCT373 in the Normal-Function Mode
Compatible With the IEEE Standard
1149.1-1990 (JTAG) Test Access Port and
Boundary-Scan Architecture
Test Operation Synchronous to Test
Access Port (TAP)
Implements Optional Test Reset Signal by
Recognizing a Double-High-Level Voltage
(10 V ) on TMS Pin
SCOPE  Instruction Set
− IEEE Standard 1149.1-1990 Required
Instructions, Optional INTEST, CLAMP
and HIGHZ
− Parallel-Signature Analysis at Inputs
− Pseudo-Random Pattern Generation
From Outputs
− Sample Inputs/ Toggle Outputs
Package Options Include Plastic
Small-Outline (DW) Packages and
Standard Plastic 300-mil DIPs (NT)
DW OR NT PACKAGE
(TOP VIEW)
LE
1Q
2Q
3Q
4Q
GND
5Q
6Q
7Q
8Q
TDO
TMS
1
24
2
23
3
22
4
21
5
20
6
19
7
18
8
17
9
16
10
15
11
14
12
13
OE
1D
2D
3D
4D
5D
VCC
6D
7D
8D
TDI
TCK
description
The SN74BCT8373 scan test device with octal D-type latches is a member of the Texas Instruments SCOPE
testability integrated circuit family. This family of devices supports IEEE Standard 1149.1-1990 boundary scan
to facilitate testing of complex circuit-board assemblies. Scan access to the test circuitry is accomplished via
the 4-wire test access port (TAP) interface.
In the normal mode, this device is functionally equivalent to the SN74F373 and SN74BCT373 octal D-type
latches. The test circuitry can be activated by the TAP to take snapshot samples of the data appearing at the
device terminals or to perform a self test on the boundary-test cells. Activating the TAP in normal mode does
not affect the functional operation of the SCOPE octal latches.
In the test mode, the normal operation of the SCOPE octal latches is inhibited and the test circuitry is enabled
to observe and control the I/O boundary of the device. When enabled, the test circuitry can perform
boundary-scan test operations as described in IEEE Standard 1149.1-1990.
Four dedicated test terminals control the operation of the test circuitry: test data input (TDI), test data output
(TDO), test mode select (TMS), and test clock (TCK). Additionally, the test circuitry performs other testing
functions such as parallel-signature analysis (PSA) on data inputs and pseudo-random pattern generation
(PRPG) from data outputs. All testing and scan operations are synchronized to the TAP interface.
The SN74BCT8373 is characterized for operation from 0°C to 70°C.
SCOPE is a trademark of Texas Instruments Incorporated.
Copyright  1994, Texas Instruments Incorporated
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2−1
SCBS471 − JUNE 1990 − REVISED JUNE 1994
FUNCTION TABLE
(normal mode, each latch)
OE
LE
D
OUTPUT
Q
L
H
H
H
L
H
L
L
L
L
X
Q0
H
X
X
Z
INPUTS
logic symbol†
TDI
TMS
TCK
14
12
13
Φ
SCAN
SN74BCT8373
TDI
TMS
TDO
11
TDO
TCK-IN
TCK-OUT
OE
LE
1D
2D
3D
4D
5D
6D
7D
8D
24
1
23
EN
C1
2
1D
22
3
21
4
20
5
19
7
17
8
16
9
15
10
† This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
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1Q
2Q
3Q
4Q
5Q
6Q
7Q
8Q
SCBS471 − JUNE 1990 − REVISED JUNE 1994
functional block diagram
Boundary-Scan Register
VCC
OE
24
VCC
LE
1
C1
VCC
1D
23
2
1D
1Q
One of Eight Channels
Bypass Register
Boundary- Control
Register
VCC
TDI
14
VCC
11
TDO
Instruction Register
VCC
TMS
12
VCC
TCK
13
TAP
Controller
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
Terminal Functions
TERMINAL
NAME
DESCRIPTION
1D −8D
Normal-function data inputs. See function table for normal-mode logic. Internal pullups force these inputs to a high level if left
unconnected.
GND
LE
Normal-function latch-enable input. See function table for normal-mode logic. An internal pullup forces LE to a high level if
left unconnected.
OE
Normal-function output-enable input. See function table for normal-mode logic. An internal pullup forces OE to a high level
if left unconnected.
1Q −8Q
2−4
Ground
Normal-function data outputs. See function table for normal-mode logic.
TCK
Test clock. One of four terminals required by IEEE Standard 1149.1-1990. Test operations of the device are synchronous to
TCK. Data is captured on the rising edge of TCK and outputs change on the falling edge of TCK. An internal pullup forces
TCK to a high level if left unconnected.
TDI
Test data input. One of four terminals required by IEEE Standard 1149.1-1990. TDI is the serial input for shifting data through
the instruction register or selected data register. An internal pullup forces TDI to a high level if left unconnected.
TDO
Test data output. One of four terminals required by IEEE Standard 1149.1-1990. TDO is the serial output for shifting data
through the instruction register or selected data register. An internal pullup forces TDO to a high level when it is not active
and is not driven from an external source.
TMS
Test mode select. One of four terminals required by IEEE Standard 1149.1-1990. TMS directs the device through its TAP
controller states. An internal pullup forces TMS to a high level if left unconnected. TMS also provides the optional test reset
signal of IEEE Standard 1149.1-1990. This is implemented by recognizing a third logic level, double high (VIHH), at TMS.
VCC
Supply voltage
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
test architecture
Serial-test information is conveyed by means of a 4-wire test bus, or TAP, that conforms to IEEE Standard
1149.1-1990. Test instructions, test data, and test control signals all are passed along this serial-test bus. The
TAP controller monitors two signals from the test bus, namely TCK and TMS. The TAP controller extracts the
synchronization (TCK) and state control (TMS) signals from the test bus and generates the appropriate on-chip
control signals for the test structures in the device. Figure 1 shows the TAP-controller state diagram.
The TAP controller is fully synchronous to the TCK signal. Input data is captured on the rising edge of TCK, and
output data changes on the falling edge of TCK. This scheme ensures that data to be captured is valid for fully
one-half of the TCK cycle.
The functional block diagram illustrates the IEEE Standard 1149.1-1990 4-wire test bus and boundary-scan
architecture and the relationship among the test bus, the TAP controller, and the test registers. As illustrated,
the device contains an 8-bit instruction register and three test-data registers: an 18-bit boundary-scan register,
a 2-bit boundary-control register, and a 1-bit bypass register.
Test-Logic-Reset
TMS = H
TMS = L
TMS = H
TMS = H
TMS = H
Run-Test/Idle
Select-DR-Scan
Select-IR-Scan
TMS = L
TMS = L
TMS = L
TMS = H
TMS = H
Capture-DR
Capture-IR
TMS = L
TMS = L
Shift-DR
Shift-IR
TMS = L
TMS = L
TMS = H
TMS = H
TMS = H
TMS = H
Exit1-DR
Exit1-IR
TMS = L
TMS = L
Pause-DR
Pause-IR
TMS = L
TMS = L
TMS = H
TMS = H
TMS = L
TMS = L
Exit2-DR
Exit2-IR
TMS = H
Update-DR
TMS = H
TMS = L
TMS = H
Update-IR
TMS = H
TMS = L
Figure 1. TAP-Controller State Diagram
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
state diagram description
The TAP controller is a synchronous finite state machine that provides test control signals throughout the device.
The state diagram is illustrated in Figure 1 and is in accordance with IEEE Standard 1149.1-1990. The TAP
controller proceeds through its states based on the level of TMS at the rising edge of TCK.
As illustrated, the TAP controller consists of 16 states. There are six stable states (indicated by a looping arrow
in the state diagram) and ten unstable states. A stable state is a state the TAP controller can retain for
consecutive TCK cycles. Any state that does not meet this criterion is an unstable state.
There are two main paths through the state diagram: one to access and control the selected data register and
one to access and control the instruction register. Only one register may be accessed at a time.
Test-Logic-Reset
The device powers up in the Test-Logic-Reset state. In the stable Test-Logic-Reset state, the test logic is reset
and is disabled so that the normal logic function of the device is performed. The instruction register is reset to
an opcode that selects the optional IDCODE instruction, if supported, or the BYPASS instruction. Certain data
registers also can be reset to their power-up values.
The state machine is constructed such that the TAP controller returns to the Test-Logic-Reset state in no more
than five TCK cycles if TMS is left high. The TMS pin has an internal pullup resistor that forces it high if left
unconnected or if a board defect causes it to be open circuited.
For the SN74BCT8373, the instruction register is reset to the binary value 11111111, which selects the BYPASS
instruction. The boundary-control register is reset to the binary value 10, which selects the PSA test operation.
Run-Test / Idle
The TAP controller must pass through the Run-Test/Idle state (from Test-Logic-Reset) before executing any test
operations. The Run-Test/Idle state also can be entered following data-register or instruction-register scans.
Run-Test/Idle is a stable state in which the test logic may be actively running a test or may be idle.
The test operations selected by the boundary-control register are performed while the TAP controller is in the
Run-Test/Idle state.
Select-DR-Scan, Select-lR-Scan
No specific function is performed in the Select-DR-Scan and Select-lR-Scan states, and the TAP controller exits
either of these states on the next TCK cycle. These states allow the selection of either data-register scan or
instruction-register scan.
Capture-DR
Upon entry to the Capture-DR state, the data register is placed in the scan path between TDI and TDO and,
on the first falling edge of TCK, TDO goes from the high-impedance state to an active state. If the TAP controller
has not passed through the Test-Logic-Reset state since the last scan operation, TDO will enable to the level
present when it was last disabled. If the TAP controller has passed through the Test-Logic-Reset state since the
last scan operation, TDO will enable to a low level.
In the Capture-DR state, the selected data register may capture a data value as specified by the current
instruction. Such capture operations occur on the rising edge of TCK upon which the TAP controller exits the
Capture-DR state.
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Shift-DR
While in the stable Shift-DR state, data is serially shifted through the selected data register on each TCK cycle.
The first shift occurs on the first rising edge of TCK after entry to the Shift-DR state (i.e., no shifting occurs during
the TCK cycle in which the TAP controller changes from Capture-DR to Shift-DR or from Exit2-DR to Shift-DR).
The last shift occurs on the rising edge of TCK upon which the TAP controller exits the Shift-DR state.
Exit1-DR, Exit2-DR
The Exit1-DR and Exit2-DR states are temporary states that end a data-register scan. It is possible to return
to the Shift-DR state from either Exit1-DR or Exit2-DR without recapturing the data register.
Pause-DR
No specific function is performed in the stable Pause-DR state, in which the TAP controller can remain
indefinitely. The Pause-DR state suspends and resumes data-register scan operations without loss of data.
Update-DR
If the current instruction calls for the selected data register to be updated with current data, then such update
occurs on the falling edge of TCK following entry to the Update-DR state, at which time TDO also goes from the
active state to the high-impedance state.
Capture-IR
In the Capture-IR state, the instruction register captures its current status value. This capture operation occurs
on the rising edge of TCK upon which the TAP controller exits the Capture-IR state.
Upon entry to the Capture-IR state, the instruction register is placed in the scan path between TDI and TDO and,
on the first falling edge of TCK, TDO goes from the high-impedance state to an active state. If the TAP controller
has not passed through the Test-Logic-Reset state since the last scan operation, TDO will enable to the level
present when it was last disabled. If the TAP controller has passed through the Test-Logic-Reset state since the
last scan operation, TDO will enable to a low level.
For the SN74BCT8373, the status value loaded in the Capture-IR state is the fixed binary value 10000001.
Shift-IR
While in the stable Shift-IR state, instruction data is serially shifted through the instruction register on each TCK
cycle. The first shift occurs on the first rising edge of TCK after entry to the Shift-IR state (i.e., no shifting occurs
during the TCK cycle in which the TAP controller changes from Capture-IR to Shift-IR or from Exit2-IR to
Shift-IR). The last shift occurs on the rising edge of TCK upon which the TAP controller exits the Shift-IR state.
Exit1-IR, Exit2-IR
The Exit1-IR and Exit2-IR states are temporary states that end an instruction-register scan. It is possible to
return to the Shift-IR state from either Exit1-IR or Exit2-IR without recapturing the instruction register.
Pause-IR
No specific function is performed in the stable Pause-IR state, in which the TAP controller can remain indefinitely.
The Pause-IR state suspends and resumes instruction-register scan operations without loss of data.
Update-IR
The current instruction is updated and takes effect on the falling edge of TCK following entry to the Update-IR
state, at which time TDO also goes from the active state to the high-impedance state.
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
register overview
With the exception of the bypass register, any test register may be thought of as a serial-shift register with a
shadow latch on each bit. The bypass register differs in that it contains only a shift register. During the
appropriate capture state (Capture-IR for instruction register, Capture-DR for data registers), the shift register
may be parallel loaded from a source specified by the current instruction. During the appropriate shift state
(Shift-IR or Shift-DR), the contents of the shift register are shifted out from TDO while new contents are shifted
in at TDI. During the appropriate update state (Update-IR or Update-DR), the shadow latches are updated from
the shift register.
instruction register description
The instruction register (IR) is eight bits long and tells the device what instruction is to be executed. Information
contained in the instruction includes the mode of operation (either normal mode, in which the device performs
its normal logic function, or test mode, in which the normal logic function is inhibited or altered), the test operation
to be performed, which of the three data registers is to be selected for inclusion in the scan path during
data-register scans, and the source of data to be captured into the selected data register during Capture-DR.
Table 2 lists the instructions supported by the SN74BCT8373. The even-parity feature specified for SCOPE
devices is not supported in this device. Bit 7 of the instruction opcode is a don’t-care bit. Any instructions that
are defined for SCOPE devices but are not supported by this device default to BYPASS.
During Capture-IR, the IR captures the binary value 10000001. As an instruction is shifted in, this value is shifted
out via TDO and can be inspected as verification that the IR is in the scan path. During Update-IR, the value
that has been shifted into the IR is loaded into shadow latches. At this time, the current instruction is updated
and any specified mode change takes effect. At power up or in the Test-Logic-Reset state, the IR is reset to the
binary value 11111111, which selects the BYPASS instruction. The IR order of scan is illustrated in Figure 2.
TDI
Bit 7
(MSB)
Don’t
Care
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Figure 2. Instruction Register Order of Scan
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Bit 1
Bit 0
(LSB)
TDO
SCBS471 − JUNE 1990 − REVISED JUNE 1994
data register description
boundary-scan register
The boundary-scan register (BSR) is 18 bits long. It contains one boundary-scan cell (BSC) for each
normal-function input pin and one BSC for each normal-function output pin. The BSR is used 1) to store test
data that is to be applied internally to the inputs of the normal on-chip logic and/or externally to the device output
terminals, and/or 2) to capture data that appears internally at the outputs of the normal on-chip logic and/or
externally at the device input terminals.
The source of data to be captured into the BSR during Capture-DR is determined by the current instruction. The
contents of the BSR may change during Run-Test/Idle as determined by the current instruction. The contents
of the BSR are not changed in Test-Logic-Reset.
The BSR order of scan is from TDI through bits 17−0 to TDO. Table 1 shows the BSR bits and their associated
device pin signals.
Table 1. Boundary-Scan-Register Configuration
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
17
LE
15
1D
7
1Q
16
OE
14
2D
6
2Q
−
−
13
3D
5
3Q
−
−
12
4D
4
4Q
−
−
11
5D
3
5Q
−
−
10
6D
2
6Q
−
−
9
7D
1
7Q
−
−
8
8D
0
8Q
boundary-control register
The boundary-control register (BCR) is two bits long. The BCR is used in the context of the RUNT instruction
to implement additional test operations not included in the basic SCOPE instruction set. Such operations
include PRPG and PSA. Table 3 shows the test operations that are decoded by the BCR.
During Capture-DR, the contents of the BCR are not changed. At power up or in Test-Logic-Reset, the BCR is
reset to the binary value 10, which selects the PSA test operation. The BCR order of scan is illustrated in
Figure 3.
TDI
Bit 1
(MSB)
Bit 0
(LSB)
TDO
Figure 3. Boundary-Control Register Order of Scan
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
bypass register
The bypass register is a 1-bit scan path that can be selected to shorten the length of the system scan path,
thereby reducing the number of bits per test pattern that must be applied to complete a test operation.
During Capture-DR, the bypass register captures a logic 0. The bypass register order of scan is illustrated in
Figure 4.
TDI
Bit 0
TDO
Figure 4. Bypass Register Order of Scan
instruction-register opcode description
The instruction-register opcodes are shown in Table 2. The following descriptions detail the operation of each
instruction.
Table 2. Instruction Register Opcodes
BINARY CODE†
BIT 7 → BIT 0
MSB → LSB
SCOPE OPCODE
DESCRIPTION
SELECTED DATA
REGISTER
EXTEST
BYPASS‡
Boundary scan
Boundary scan
Test
X0000001
Bypass scan
Bypass
Normal
X0000010
SAMPLE/PRELOAD
Sample boundary
Boundary scan
Normal
X0000011
Boundary scan
Boundary scan
Test
X0000100
INTEST
BYPASS‡
Bypass scan
Bypass
Normal
X0000101
BYPASS‡
Bypass scan
Bypass
Normal
X0000110
HIGHZ (TRIBYP)
Control boundary to high impedance
Bypass
Modified test
X0000111
CLAMP (SETBYP)
BYPASS‡
Control boundary to 1/0
Bypass
Test
X0001000
Bypass scan
Bypass
Normal
X0001001
RUNT
Boundary run test
Bypass
Test
X0001010
READBN
Boundary read
Boundary scan
Normal
X0001011
READBT
Boundary read
Boundary scan
Test
X0001100
CELLTST
Boundary self test
Boundary scan
Normal
X0001101
TOPHIP
Boundary toggle outputs
Bypass
Test
X0001110
SCANCN
Boundary-control register scan
Boundary control
Normal
X0001111
SCANCT
Boundary-control register scan
Boundary control
Test
All others
BYPASS
Bypass scan
Bypass
Normal
X0000000
† Bit 7 is a don’t-care bit; X = don’t care.
‡ The BYPASS instruction is executed in lieu of a SCOPE instruction that is not supported in the SN74BCT8373.
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MODE
SCBS471 − JUNE 1990 − REVISED JUNE 1994
boundary scan
This instruction conforms to the IEEE Standard 1149.1-1990 EXTEST and INTEST instructions. The BSR is
selected in the scan path. Data appearing at the device input terminals is captured in the input BSCs, while data
appearing at the outputs of the normal on-chip logic is captured in the output BSCs. Data that has been scanned
into the input BSCs is applied to the inputs of the normal on-chip logic, while data that has been scanned into
the output BSCs is applied to the device output terminals. The device operates in the test mode.
bypass scan
This instruction conforms to the IEEE Standard 1149.1-1990 BYPASS instruction. The bypass register is
selected in the scan path. A logic 0 value is captured in the bypass register during Capture-DR. The device
operates in the normal mode.
sample boundary
This instruction conforms to the IEEE Standard 1149.1-1990 SAMPLE/PRELOAD instruction. The BSR is
selected in the scan path. Data appearing at the device input terminals is captured in the input BSCs, while data
appearing at the outputs of the normal on-chip logic is captured in the output BSCs. The device operates in the
normal mode.
control boundary to high impedance
This instruction conforms to the IEEE Standard 1149.1a-1993 HIGHZ instruction. The bypass register is
selected in the scan path. A logic 0 value is captured in the bypass register during Capture-DR. The device
operates in a modified test mode in which all device output terminals are placed in the high-impedance state,
the device input terminals remain operational, and the normal on-chip logic function is performed.
control boundary to 1/0
This instruction conforms to the IEEE Standard 1149.1a-1993 CLAMP instruction. The bypass register is
selected in the scan path. A logic 0 value is captured in the bypass register during Capture-DR. Data in the input
BSCs is applied to the inputs of the normal on-chip logic, while data in the output BSCs is applied to the device
output terminals. The device operates in the test mode.
boundary run test
The bypass register is selected in the scan path. A logic 0 value is captured in the bypass register during
Capture-DR. The device operates in the test mode. The test operation specified in the BCR is executed during
Run-Test/Idle. The four test operations decoded by the BCR are: sample inputs/toggle outputs (TOPSIP),
PRPG, PSA, and simultaneous PSA and PRPG (PSA/PRPG).
boundary read
The BSR is selected in the scan path. The value in the BSR remains unchanged during Capture-DR. This
instruction is useful for inspecting data after a PSA operation.
boundary self test
The BSR is selected in the scan path. All BSCs capture the inverse of their current values during Capture-DR.
In this way, the contents of the shadow latches may be read out to verify the integrity of both shift-register and
shadow-latch elements of the BSR. The device operates in the normal mode.
boundary toggle outputs
The bypass register is selected in the scan path. A logic 0 value is captured in the bypass register during
Capture-DR. Data in the shift register elements of the selected output BSCs is toggled on each rising edge of
TCK in Run-Test/Idle and is then updated in the shadow latches and applied to the associated device output
terminals on each falling edge of TCK in Run-Test/Idle. Data in the selected input BSCs remains constant and
is applied to the inputs of the normal on-chip logic. Data appearing at the device input terminals is not captured
in the input BSCs. The device operates in the test mode.
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SCBS471 − JUNE 1990 − REVISED JUNE 1994
boundary-control-register scan
The BCR is selected in the scan path. The value in the BCR remains unchanged during Capture-DR. This
operation must be performed before a boundary-run test operation to specify which test operation is to be
executed.
boundary-control-register opcode description
The BCR opcodes are decoded from BCR bits 1 −0 as shown in Table 3. The selected test operation is
performed while the RUNT instruction is executed in the Run-Test/Idle state. The following descriptions detail
the operation of each BCR instruction and illustrate the associated PSA and PRPG algorithms.
Table 3. Boundary-Control-Register Opcodes
BINARY CODE
BIT 1 → BIT 0
MSB → LSB
DESCRIPTION
00
Sample inputs/toggle outputs (TOPSIP)
01
Pseudo-random pattern generation / 16-bit mode (PRPG)
10
Parallel-signature analysis / 16-bit mode (PSA)
11
Simultaneous PSA and PRPG / 8-bit mode (PSA/PRPG)
It should be noted, in general, that while the control input BSCs (bits 17 −16) are not included in the sample,
toggle, PSA, or PRPG algorithms, the output-enable BSC (bit 16 of the BSR) does control the drive state (active
or high impedance) of the device output terminals.
sample inputs / toggle outputs (TOPSIP)
Data appearing at the device input terminals is captured in the shift-register elements of the input BSCs on each
rising edge of TCK. This data is then updated in the shadow latches of the input BSCs and applied to the inputs
of the normal on-chip logic. Data in the shift register elements of the output BSCs is toggled on each rising edge
of TCK, updated in the shadow latches, and applied to the device output terminals on each falling edge of TCK.
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pseudo-random pattern generation (PRPG)
A pseudo-random pattern is generated in the shift-register elements of the BSCs on each rising edge of TCK
and then updated in the shadow latches and applied to the device output terminals on each falling edge of TCK.
This data also is updated in the shadow latches of the input BSCs and applied to the inputs of the normal on-chip
logic. Figure 5 illustrates the 16-bit linear-feedback shift-register algorithm through which the patterns are
generated. An initial seed value should be scanned into the BSR before performing this operation. A seed value
of all zeroes will not produce additional patterns.
1D
2D
3D
4D
5D
6D
7D
8D
1Q
2Q
3Q
4Q
5Q
6Q
7Q
8Q
=
Figure 5. 16-Bit PRPG Configuration
parallel-signature analysis (PSA)
Data appearing at the device input terminals is compressed into a 16-bit parallel signature in the shift-register
elements of the BSCs on each rising edge of TCK. This data is then updated in the shadow latches of the input
BSCs and applied to the inputs of the normal on-chip logic. Data in the shadow latches of the output BSCs
remains constant and is applied to the device outputs. Figure 6 illustrates the 16-bit linear-feedback shift-register
algorithm through which the signature is generated. An initial seed value should be scanned into the BSR before
performing this operation.
1D
2D
3D
4D
5D
6D
7D
8D
1Q
2Q
3Q
4Q
5Q
6Q
7Q
8Q
=
=
Figure 6. 16-Bit PSA Configuration
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•
2−13
SCBS471 − JUNE 1990 − REVISED JUNE 1994
simultaneous PSA and PRPG (PSA / PRPG)
Data appearing at the device input terminals is compressed into an 8-bit parallel signature in the shift-register
elements of the input BSCs on each rising edge of TCK. This data is then updated in the shadow latches of the
input BSCs and applied to the inputs of the normal on-chip logic. At the same time, an 8-bit pseudo-random
pattern is generated in the shift-register elements of the output BSCs on each rising edge of TCK, updated in
the shadow latches, and applied to the device output terminals on each falling edge of TCK. Figure 7 illustrates
the 8-bit linear-feedback shift-register algorithm through which the signature and patterns are generated. An
initial seed value should be scanned into the BSR before performing this operation. A seed value of all zeroes
will not produce additional patterns.
1D
2D
3D
4D
5D
6D
7D
8D
1Q
2Q
3Q
4Q
5Q
6Q
7Q
8Q
=
=
Figure 7. 8-Bit PSA / PRPG Configuration
2−14
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•
SCBS471 − JUNE 1990 − REVISED JUNE 1994
timing description
All test operations of the SN74BCT8373 are synchronous to TCK. Data on the TDI, TMS, and normal-function
inputs is captured on the rising edge of TCK. Data appears on the TDO and normal-function output terminals
on the falling edge of TCK. The TAP controller is advanced through its states (as illustrated in Figure 1) by
changing the value of TMS on the falling edge of TCK and then applying a rising edge to TCK.
A simple timing example is illustrated in Figure 8. In this example, the TAP controller begins in the
Test-Logic-Reset state and is advanced through its states as necessary to perform one instruction-register scan
and one data-register scan. While in the Shift-IR and Shift-DR states, TDI is used to input serial data and TDO
is used to output serial data. The TAP controller is then returned to the Test-Logic-Reset state. Table 4 explains
the operation of the test circuitry during each TCK cycle.
Table 4. Explanation of Timing Example
TCK
CYCLE(S)
TAP STATE
AFTER TCK
DESCRIPTION
1
Test-Logic-Reset
TMS is changed to a logic 0 value on the falling edge of TCK to begin advancing the TAP controller toward
the desired state.
2
Run-Test/Idle
3
Select-DR-Scan
4
Select-IR-Scan
5
Capture-IR
TDO becomes active on the falling edge of TCK. The IR captures the 8-bit binary value 10000001 on the rising
edge of TCK as the TAP controller exits the Capture-IR state.
6
Shift-IR
TDI is made valid on the falling edge of TCK. The first bit is shifted into the TAP on the rising edge of TCK as
the TAP controller advances to the next state.
7−13
Shift-IR
One bit is shifted into the IR on each TCK rising edge. With TDI held at a logic 1 value, the 8-bit binary value
11111111 is serially scanned into the IR. At the same time, the 8-bit binary value 10000001 is serially scanned
out of the IR via TDO. In TCK cycle 13, TMS is changed to a logic 1 value to end the IR scan on the next TCK
cycle. The last bit of the instruction is shifted as the TAP controller advances from Shift-IR to Exit1-IR.
14
Exit1-IR
15
Update-IR
16
Select-DR-Scan
17
Capture-DR
TDO becomes active on the falling edge of TCK. The bypass register captures a logic 0 value on the rising
edge of TCK as the TAP controller exits the Capture-DR state.
18
Shift-DR
TDO becomes active and TDI is made valid on the falling edge of TCK. The first bit is shifted into the TAP on
the rising edge of TCK as the TAP controller advances to the next state.
19 −20
Shift-DR
The binary value 101 is shifted in via TDI, while the binary value 010 is shifted out via TDO.
21
Exit1-DR
22
Update-DR
23
Select-DR-Scan
24
Select-IR-Scan
25
Test-Logic-Reset
The IR is updated with the new instruction (BYPASS) and TDO becomes inactive (goes to the high-impedance
state) on the falling edge of TCK.
In general, the selected data register is updated with the new data and TDO becomes inactive (goes to the
high-impedance state) on the falling edge of TCK.
Test operation completed
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•
2−15
SCBS471 − JUNE 1990 − REVISED JUNE 1994
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
TCK
Test-Logic-Reset
Select-IR-Scan
Select-DR-Scan
Exit1-DR
Update-DR
ÌÌÌÌÌÌ
ÌÌÌÌÌÌ
ÌÌÌÌÌ
ÌÌÌÌÌ
Shift-DR
Capture-DR
Exit1-IR
Select-DR-Scan
ÌÌ
ÌÌ
Update-IR
ÌÌÌÌÌ
ÌÌÌÌÌ
ÌÌÌ
ÌÌÌ
Shift-IR
Capture-IR
Select-IR-Scan
TAP
Controller
State
Select-DR-Scan
TDO
ÌÌÌÌÌÌÌÌ
ÌÌÌÌÌÌÌÌ
ÌÌÌÌÌÌÌ
ÌÌÌÌÌÌÌ
Run-Test/Idle
TDI
Test-Logic-Reset
TMS
3-State (TDO) or Don’t Care (TDI)
Figure 8. Timing Example
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5 V to 7 V
Input voltage range, VI: except TMS (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5 V to 7 V
TMS (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5 V to 12 V
Voltage range applied to any output in the disabled or power-off state . . . . . . . . . . . . . . . . . . . −0.5 V to 5.5 V
Voltage range applied to any output in the high state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5 V to VCC
Input clamp current, IIK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −30 mA
Current into any output in the low state: TDO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 mA
Any Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 mA
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −65°C to 150°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: The input voltage rating may be exceeded if the input clamp-current rating is observed.
recommended operating conditions
MIN
NOM
MAX
4.5
5
5.5
UNIT
VCC
VIH
Supply voltage
VIHH
VIL
Double-high-level input voltage
Low-level input voltage
0.8
V
IIK
Input clamp current
−18
mA
IOH
High-level output current
IOL
Low-level output current
TA
Operating free-air temperature
High-level input voltage
2
TMS
10
TDO
2−16
•
12
−15
TDO
24
Any Q
64
0
•
V
V
−3
Any Q
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V
70
mA
mA
°C
SCBS471 − JUNE 1990 − REVISED JUNE 1994
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
VIK
Any Q
VOH
TEST CONDITIONS
II = − 18 mA
IOH = − 3 mA
2.7
3.4
2.4
3.4
VCC = 4.5 V
IOH = − 3 mA
IOH = − 15 mA
2
3.1
IOH = − 1 mA
IOH = − 1 mA
2.7
3.4
2.5
3.4
IOH = − 3 mA
IOL = 64 mA
2.4
VCC = 4.5 V
Any Q
VOL
TDO
II
IIH
IIHH
IIL
VCC = 4.5 V
VCC = 5.5 V,
VCC = 5.5 V,
TMS
TYP†
VCC = 4.5 V,
VCC = 4.75 V,
VCC = 4.75 V,
TDO
MIN
VCC = 5.5 V,
VCC = 5.5 V,
IOL = 24 mA
VI = 5.5 V
TDO
IOS‡
ICC
TDO
V
V
3.3
0.55
0.35
0.5
−35
−100
µA
1
mA
−200
µA
0.1
VI = 2.7 V
VI = 10 V
−1
VI = 0.5 V
−70
50
VCC = 5.5 V,
VO = 2.7 V
VCC = 5.5 V,
VO = 0.5 V
VCC = 5.5 V,
VO = 0
−1
−35
−100
−70
−200
Any Q
IOZL
UNIT
−1.2
0.42
Any Q
IOZH
MAX
−50
VCC = 5.5 V,
−100
Outputs open
−225
Outputs high
3.5
7
Outputs low
35
52
Outputs disabled
1.5
3.5
Ci
VCC = 5 V,
VI = 2.5 V or 0.5 V
10
Co
VCC = 5 V,
VO = 2.5 V or 0.5 V
14
† All typical values are at VCC = 5 V, TA = 25°C.
‡ Not more than one output should be shorted at a time, and the duration of the short circuit should not exceed one second.
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•
V
mA
µA
A
A
µA
mA
mA
pF
pF
2−17
SCBS471 − JUNE 1990 − REVISED JUNE 1994
timing requirements over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (normal mode) (see Figure 9)
VCC = 5 V,
TA = 25°C
MIN
MIN
MAX
UNIT
MAX
tw
tsu
Pulse duration
LE high
5
5
ns
Setup time
Data before LE↓
3
3
ns
th
Hold time
Data after LE↓
2
2
ns
timing requirements over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (test mode) (see Figure 9)
VCC = 5 V,
TA = 25°C
fclock
Clock frequency
tw
Pulse duration
tsu
Setup time
th
Hold time
td
Delay time
TCK
MAX
0
20
MIN
MAX
UNIT
0
20
MHz
TCK high or low
25
25
TMS double high
50
50
Any D before TCK↑
6
6
LE or OE before TCK↑
6
6
TDI before TCK↑
6
6
TMS before TCK↑
15
15
Any D after TCK↑
4.5
4.5
LE or OE after TCK↑
4.5
4.5
TDI after TCK↑
4.5
4.5
TMS after TCK↑
2−18
MIN
Power up to TCK↑
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•
0
0
100
100
ns
ns
ns
ns
SCBS471 − JUNE 1990 − REVISED JUNE 1994
switching characteristics over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (normal mode) (see Figure 9)
FROM
(INPUT)
TO
(OUTPUT)
tPLH
tPHL
D
Q
tPLH
tPHL
LE
Q
tPZH
tPZL
OE
Q
tPHZ
tPLZ
OE
Q
PARAMETER
VCC = 5 V,
TA = 25°C
MIN
MAX
9
2
10
5.5
9
2
10
3
6.7
10.5
3
11.4
3
6.7
10.5
3
11.6
2.4
5.6
9
2.4
10.6
3
6.8
10.9
3
12
2.5
5.7
9.5
2.5
10
2.4
5.5
9
2.4
9.5
MIN
TYP
MAX
2
5.6
2
UNIT
ns
ns
ns
ns
switching characteristics over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (test mode) (see Figure 9)
PARAMETER
fmax
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
tPZH
tPZL
tPZH
tPZL
tPZH
tPZL
tPHZ
tPLZ
tPHZ
tPLZ
tPHZ
tPLZ
FROM
(INPUT)
TO
(OUTPUT)
VCC = 5 V,
TA = 25°C
MIN
MIN
MAX
3.9
10.9
15.7
3.9
19.8
3.9
10.8
15.3
3.9
19.5
3.2
8.5
12.3
3.2
15.4
3.2
8.3
12
3.2
15
6.2
13.7
21
6.2
25
6.6
15
22
6.6
26
4.7
11.7
16.7
4.7
21.1
5.5
13.6
19.7
5.5
22.9
2.4
6.2
9
2.4
10.8
3.2
7.6
10.6
3.2
12.6
6.9
15.5
21.7
6.9
27
7.8
17.6
24.9
7.8
29
3.4
9
13.2
3.4
17.3
3.6
10
14.6
3.6
17.8
2.6
7.1
10.2
2.6
12.8
2.2
5.9
8.7
2.2
11.6
5
12.7
18.3
5
22.8
4.6
12.2
17.5
4.6
22
20
TCK↓
Q
TCK↓
TDO
TCK↑
Q
TCK↓
Q
TCK↓
TDO
TCK↑
Q
TCK↓
Q
TCK↓
TDO
TCK↑
Q
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•
MAX
TYP
20
UNIT
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
2−19
SCBS471 − JUNE 1990 − REVISED JUNE 1994
PARAMETER MEASUREMENT INFORMATION
7 V (tPZL, tPLZ, O.C.)
S1
Open
(all others)
From Output
Under Test
Test
Point
CL
(see Note A)
R1
From Output
Under Test
R1
Test
Point
CL
(see Note A)
R2
LOAD CIRCUIT FOR
TOTEM-POLE OUTPUTS
RL = R1 = R2
LOAD CIRCUIT FOR
3-STATE AND OPEN-COLLECTOR OUTPUTS
High-Level
Pulse
(see Note B)
3V
Timing Input
(see Note B)
3V
1.5 V
1.5 V
0V
1.5 V
tw
0V
Data Input
(see Note B)
3V
th
tsu
Low-Level
Pulse
3V
1.5 V
1.5 V
0V
1.5 V
1.5 V
VOLTAGE WAVEFORMS
PULSE DURATION
0V
VOLTAGE WAVEFORMS
SETUP AND HOLD TIMES
3V
3V
Input
(see Note B)
1.5 V
1.5 V
0V
tPLH
In-Phase
Output
(see Note D)
VOH
1.5 V
1.5 V
VOL
VOH
1.5 V
1.5 V
0V
tPLZ
1.5 V
Waveform 1
(see Notes C and D)
3.5 V
VOL
tPHZ
tPLH
1.5 V
1.5 V
tPZL
tPHL
tPHL
Out-of-Phase
Output
(see Note D)
Output
Control
(low-level enable)
0.3 V
tPZH
Waveform 2
(see Notes C and D)
VOL
VOLTAGE WAVEFORMS
PROPAGATION DELAY TIMES (see Note D)
VOH
1.5 V
0.3 V
0V
VOLTAGE WAVEFORMS
ENABLE AND DISABLE TIMES, 3-STATE OUTPUTS
NOTES: A. CL includes probe and jig capacitance.
B. All input pulses are supplied by generators having the following characteristics: PRR ≤ 10 MHz, tr = tf ≤ 2.5 ns, duty cycle = 50%.
C. Waveform 1 is for an output with internal conditions such that the output is low except when disabled by the output control.
Waveform 2 is for an output with internal conditions such that the output is high except when disabled by the output control.
D. The outputs are measured one at a time with one transition per measurement.
E. When measuring propagation delay times of 3-state outputs, switch S1 is open.
Figure 9. Load Circuits and Voltage Waveforms
2−20
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