Texas Instruments SN74ABT18502PM Datasheet
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
• Members of the Texas Instruments
SCOPE
Family of Testability Products
• Members of the Texas Instruments
Widebus
Family
• Compatible With the IEEE Standard
1149.1-1990 (JTAG) Test Access Port and
Boundary-Scan Architecture
•
UBT
(Universal Bus Transceiver)
Combines D-Type Latches and D-Type
Flip-Flops for Operation in Transparent,
Latched, or Clocked Mode
• Two Boundary-Scan Cells per I/O for
Greater Flexibility
• State-of-the-Art
Significantly Reduces Power Dissipation
EPIC-ΙΙB
1A3
1A4
1A5
GND
1A6
1A7
1A8
1A9
NC
V
CC
2A1
2A2
2A3
GND
2A4
2A5
2A6
BiCMOS Design
1A2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
28 29 30 31 32 33 34
SN54ABT18502 . . . HV PACKAGE
1A1
1OEAB
GND
87 65493168672
1LEAB
1CLKAB
(TOP VIEW)
CC
VNCTMS
TDO
35 36 37 38 39
•
SCOPE
Instruction Set
– IEEE Standard 1149.1-1990 Required
Instructions, Optional INTEST, and
P1149.1A CLAMP and HIGHZ
– Parallel Signature Analysis at Inputs With
Masking Option
– Pseudo-Random Pattern Generation
From Outputs
– Sample Inputs/Toggle Outputs
– Binary Count From Outputs
– Device Identification
– Even-Parity Opcodes
• Packaged in 64-Pin Plastic Thin Quad Flat
Pack Using 0.5-mm Center-to-Center
Spacings and 68-Pin Ceramic Quad Flat
Pack Using 25-mil Center-to-Center
Spacings
1CLKBA
1LEBA
1OEBA
GND
1B1
1B2
1B3
66 652764 63 62 61
1B4
60
1B5
59
1B6
58
GND
57
1B7
56
1B8
55
1B9
54
V
53
CC
NC
52
2B1
51
2B2
50
2B3
49
2B4
48
GND
47
2B5
46
2B6
45
2B7
44
40 41 42 43
CC
NC
2LEAB
2CLKAB
TDI
V
TCK
2LEBA
2CLKBA
2A9
2A7
2A8
GND
2OEAB
NC – No internal connection
SCOPE, Widebus, UBT, and EPIC-IIB are trademarks of T exas Instruments Incorporated.
UNLESS OTHERWISE NOTED this document contains PRODUCTION
DATA information current as of publication date. Products conform to
specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all
parameters.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
GND
2B9
2B8
2OEBA
Copyright 1993, Texas Instruments Incorporated
1
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
1A3
1A4
1A5
GND
1A6
1A7
1A8
1A9
V
CC
2A1
2A2
2A3
GND
2A4
2A5
2A6
SN74ABT18502 ...PM PACKAGE
1OEAB
1A2
1A1
63 62 61 60 5964 58 56 55 5457
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
18 19
20
GND
1CLKAB
1LEAB
21 22 23 24
(TOP VIEW)
CC
TDO
V
TMS
25 26 27 28 29
1LEBA
1OEBA
1CLKBA
53 521751 50 49
1B1
GND
30 31 32
1B2
1B3
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
1B4
1B5
1B6
GND
1B7
1B8
1B9
V
CC
2B1
2B2
2B3
2B4
GND
2B5
2B6
2B7
CC
2LEAB
2CLKAB
TDI
V
TCK
2CLKBA
GND
2LEBA
2B9
2OEBA
2B8
2A7
2A8
2A9
GND
2OEAB
description
The SN54ABT18502 and SN74ABT18502 scan test devices with 18-bit universal bus transceivers are
members of the T exas Instruments SCOPE testability IC 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, these devices are 18-bit universal bus transceivers that combine D-type latches and D-type
flip-flops to allow data flow in transparent, latched, or clocked modes. They can be used either as two 9-bit
transceivers or one 18-bit transceiver. The test circuitry can be activated by the TAP to take snapshot samples
of the data appearing at the device pins or to perform a self test on the boundary test cells. Activating the T AP
in the normal mode does not affect the functional operation of the SCOPE universal bus transceivers.
Data flow in each direction is controlled by output-enable (OEAB
and clock (CLKAB and CLKBA) inputs. For A-to-B data flow, the device operates in the transparent mode when
LEAB is high. When LEAB is low , the A-bus data is latched while CLKAB is held at a static low or high logic level.
Otherwise, if LEAB is low, A-bus data is stored on a low-to-high transition of CLKAB. When OEAB is low, the
B outputs are active. When OEAB
is high, the B outputs are in the high-impedance state. B-to-A data flow is
similar to A-to-B data flow but uses the OEBA, LEBA, and CLKBA inputs.
In the test mode, the normal operation of the SCOPE universal bus transceivers is inhibited, and the test
circuitry is enabled to observe and control the I/O boundary of the device. When enabled, the test circuitry
performs boundary scan test operations according to the protocol described in IEEE Standard 1149.1-1990.
and OEBA), latch-enable (LEAB and LEBA),
2 2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
description (continued)
Four dedicated test pins are used to observe and 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 can perform
other testing functions such as parallel signature analysis on data inputs and pseudo-random pattern generation
from data outputs. All testing and scan operations are synchronized to the TAP interface.
Additional flexibility is provided in the test mode through the use of two boundary scan cells (BSCs) for each
I/O pin. This allows independent test data to be captured and forced at either bus (A or B). A PSA/COUNT
instruction is also included to ease the testing of memories and other circuits where a binary count addressing
scheme is useful.
The SN54ABT18502 is characterized for operation over the full military temperature range of –55°C to 125°C.
The SN74ABT18502 is characterized for operation from –40°C to 85°C.
FUNCTION TABLE
(normal mode, each register)
INPUTS
OEAB LEAB CLKAB A
L L L X B
L L ↑ LL
L L ↑ HH
L HXLL
L HXHH
H X X X Z
†
A-to-B data flow is shown. B-to-A data flow is similar
but uses OEBA
‡
Output level before the indicated steady-state input
conditions were established.
, LEBA, and CLKBA.
†
OUTPUT
B
‡
0
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
3
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
functional block diagram
Boundary-Scan Register
1LEAB
60
1CLKAB
1OEAB
1LEBA
1CLKBA
1OEBA
1A1
2LEAB
2CLKAB
2OEAB
2LEBA
2CLKBA
2OEBA
2A1
59
62
54
55
53
63
22
23
21
28
27
30
10
One of Nine Channels
One of Nine Channels
C1
1D
C1
1D
1D
1D
C1
C1
C1
1D
C1
1D
C1
1D
C1
1D
51
40
1B1
2B1
V
CC
24
TDI
V
CC
56
TMS
26
TCK
Pin numbers shown are for the PM package.
4 4
Controller
Bypass Register
Boundary-Control
Register
Identification
Register
Instruction
Register
TAP
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58
TDO
18-BIT REGISTERED BUS TRANSCEIVERS
Terminal Functions
PIN NAME DESCRIPTION
GND Ground
TCK
TDI
TDO
TMS
V
CC
1A1–1A9,
2A1–2A9
1B1–1B9,
2B1–2B9
1CLKAB, 1CLKBA,
2CLKAB, 2CLKBA
1LEAB, 1LEBA,
2LEAB, 2LEBA
1OEAB, 1OEBA,
, 2OEBA
2OEAB
Test clock. One of four pins required by IEEE Standard 1149.1-1990. Test operations of the device are synchronous to
the test clock. Data is captured on the rising edge of TCK and outputs change on the falling edge of TCK.
T est data input. One of four pins required by IEEE Standard 1 149.1-1990. The test data input 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.
Test data output. One of four pins required by IEEE Standard 1149.1-1990. The test data output is the serial output for
shifting data through the instruction register or selected data register.
T est mode select. One of four pins required by IEEE Standard 1 149.1-1990. The test mode select input directs the device
through its test access port (TAP) controller states. An internal pullup forces TMS to a high level if left unconnected.
Supply voltage
Normal-function A-bus I/O ports. See function table for normal-mode logic.
Normal-function B-bus I/O ports. See function table for normal-mode logic.
Normal-function clock inputs. See function table for normal-mode logic.
Normal-function latch enables. See function table for normal-mode logic.
Normal-function output enables. See function table for normal-mode logic.
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
5
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
test architecture
Serial test information is conveyed by means of a 4-wire test bus or test access port (T AP), that conforms to IEEE
Standard 1 149.1-1990. Test instructions, test data, and test control signals are all passed along this serial test
bus. The T AP controller monitors two signals from the test bus, namely TCK and TMS. The function of the T AP
controller is to extract the synchronization (TCK) and state control (TMS) signals from the test bus and generate
the appropriate on-chip control signals for the test structures in the device. Figure 1 shows the T AP controller
state diagram.
The T AP 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 between the test bus, the T AP controller , and the test registers. As illustrated,
the device contains an 8-bit instruction register and four test data registers: an 84-bit boundary-scan register,
a 21-bit boundary-control register, a 1-bit bypass register, and a 32-bit device identification register.
Test-Logic-Reset
TMS = H
TMS = L
TMS = L
Run-Test/Idle Select-DR-Scan
TMS = L
Capture-DR
TMS = L
Shift-DR
TMS = L
TMS = H
TMS = H
Exit1-DR
TMS = L
Pause-DR
TMS = L
TMS = H
Exit2-DR
TMS = H
TMS = HTMS = H
TMS = H TMS = H
TMS = L
TMS = L
Select-IR-Scan
TMS = H
TMS = L
Capture-IR
TMS = L
Shift-IR
TMS = L
TMS = H
TMS = H
Exit1-IR
TMS = L
Pause-IR
TMS = L
TMS = H
Exit2-IR
TMS = H
Update-DR
TMS = LTMS = H
Update-IR
TMS = LTMS = H
Figure 1. TAP Controller State Diagram
6 6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
state diagram description
The test access port (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 T AP controller consists of sixteen states. There are six stable states (indicated by a looping
arrow in the state diagram) and ten unstable states. A stable state is defined as a state the T AP controller can
retain for consecutive TCK cycles. Any state that does not meet this criterion is an unstable state.
There are two main paths though the state diagram: one to access and control the selected data register and
one to access and control the instruction register. Only one register can 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 BYP ASS instruction. Certain data
registers may also be reset to their power-up values.
The state machine is constructed such that the T AP 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 ′ABT18502, the instruction register is reset to the binary value 10000001, which selects the IDCODE
instruction. Each bit in the boundary-scan register is reset to logic 0 except bits 83–80, which are reset to logic 1.
The boundary-control register is reset to the binary value 000000000000000000010, which selects the PSA test
operation with no input masking.
Run-Test/Idle
The T AP controller must pass through the Run-T est/Idle state (from T est-Logic-Reset) before executing any test
operations. The Run-Test/Idle state can also be entered following data register or instruction register scans.
Run-Test/Idle is provided as a stable state in which the test logic may be actively running a test or can be idle.
The test operations selected by the boundary-control register are performed while the T AP 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 T AP controller exits
either of these states on the next TCK cycle. These states are provided to allow the selection of either data
register scan or instruction register scan.
Capture-DR
When a data register scan is selected, the TAP controller must pass through the Capture-DR state. In the
Capture-DR state, the selected data register can capture a data value as specified by the current instruction.
Such capture operations occur on the rising edge of TCK upon which the T AP controller exits the Capture-DR
state.
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7
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
state diagram description (continued)
Shift-DR
Upon entry to the Shift-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. TDO enables to the logic
level present in the least significant bit of the selected data register.
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 T AP 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 used to 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.
On the first falling edge of TCK after entry to Exit1-DR, TDO goes from the active state to the high-impedance
state.
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 provides the capability of suspending and resuming 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, such update occurs
on the falling edge of TCK following entry to the Update-DR state.
Capture-IR
When an instruction register scan is selected, the T AP controller must pass through the Capture-IR state. 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.
For the ′ABT18502, the status value loaded in the Capture-IR state is the fixed binary value 10000001.
Shift-IR
Upon entry to the Shift-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. TDO enables to
the logic level present in the least significant bit of the instruction register.
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 T AP controller exits the Shift-IR state.
Exit1-IR, Exit2-IR
The Exit1-IR and Exit2-IR states are temporary states used to 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.
On the first falling edge of TCK after entry to Exit1-IR, TDO goes from the active state to the high-impedance
state.
8 8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
SN54ABT18502, SN74ABT18502
SCAN TEST DEVICES WITH
18-BIT REGISTERED BUS TRANSCEIVERS
SCBS109B – AUGUST 1992 – REVISED JUNE 1993
state diagram description (continued)
Pause-IR
No specific function is performed in the stable Pause-IR state, in which the T AP controller can remain indefinitely.
The Pause-IR state provides the capability of suspending and resuming 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.
register overview
With the exception of the bypass and device identification registers, any test register can be thought of as a serial
shift register with a shadow latch on each bit. The bypass and device identification registers differ in that they
contain 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 is used to tell 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 four 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 4 lists the instructions supported by the ′ABT18502. The even-parity feature specified for SCOPE
devices is supported in this device. Bit 7 of the instruction opcode is the parity 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 will be
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 10000001, which selects the IDCODE instruction.
The instruction register order of scan is illustrated in Figure 2.
Bit 7
Parity
(MSB)
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Figure 2. Instruction Register Order of Scan
Bit 0
(LSB)
TDOTDI
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9
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