SN54LVTH18504A, SN54LVTH182504A, SN74LVTH18504A, SN74LVTH182504A

3.3-V ABT SCAN TEST DEVICES

WITH 20-BIT UNIVERSAL BUS TRANSCEIVERS

SCBS667B – JULY 1996 – REVISED JUNE 1997

10

POST OFFICE BOX 655303

data register description

boundary-scan register

The boundary-scan register (BSR) is 48 bits long. It contains one boundary-scan cell (BSC) for each

normal-function input pin and one BSC for each normal-function I/O pin (one single cell for both input data and

output data). The BSR is used to store test data that is to be applied externally to the device output pins, and/or

to capture data that appears internally at the outputs of the normal on-chip logic and/or externally at the device

input pins.

The source of data to be captured into the BSR during Capture-DR is determined by the current instruction. The

contents of the BSR can change during Run-Test/Idle as determined by the current instruction. At power up or

in Test-Logic-Reset, BSCs 47–46 are reset to logic 1, ensuring that these cells, which control A-port and B-port

outputs, are set to benign values (i.e., if test mode were invoked, the outputs would be at high-impedance state).

Reset values of other BSCs should be considered indeterminate.

The BSR order of scan is from TDI through bits 47–0 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

47

OEAB

39

A20-I/O

19

B20-I/O

46

OEBA

38

A19-I/O

18

B19-I/O

45

CLKAB

37

A18-I/O

17

B18-I/O

44

CLKBA

36

A17-I/O

16

B17-I/O

43

CLKENAB

35

A16-I/O

15

B16-I/O

42

CLKENBA

34

A15-I/O

14

B15-I/O

41

LEAB

33

A14-I/O

13

B14-I/O

40

LEBA

32

A13-I/O

12

B13-I/O

––

––

31

A12-I/O

11

B12-I/O

––

––

30

A11-I/O

10

B11-I/O

––

––

29

A10-I/O

9

B10-I/O

––

––

28

A9-I/O

8

B9-I/O

––

––

27

A8-I/O

7

B8-I/O

––

––

26

A7-I/O

6

B7-I/O

––

––

25

A6-I/O

5

B6-I/O

––

––

24

A5-I/O

4

B5-I/O

––

––

23

A4-I/O

3

B4-I/O

––

––

22

A3-I/O

2

B3-I/O

––

––

21

A2-I/O

1

B2-I/O

––

––

20

A1-I/O

0

B1-I/O