SN54LVT18502

3.3-V ABT SCAN TEST DEVICE

WITH 18-BIT UNIVERSAL BUS TRANSCEIVERS

SCBS669 – JULY 1996

9

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 1) to store test data that is to be applied externally to the device output pins,

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 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 47–44 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 the

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

2OEAB

35

2A9-I/O

17

2B9-I/O

46

1OEAB

34

2A8-I/O

16

2B8-I/O

45

2OEBA

33

2A7-I/O

15

2B7-I/O

44

1OEBA

32

2A6-I/O

14

2B6-I/O

43

2CLKAB

31

2A5-I/O

13

2B5-I/O

42

1CLKAB

30

2A4-I/O

12

2B4-I/O

41

2CLKBA

29

2A3-I/O

11

2B3-I/O

40

1CLKBA

28

2A2-I/O

10

2B2-I/O

39

2LEAB

27

2A1-I/O

9

2B1-I/O

38

1LEAB

26

1A9-I/O

8

1B9-I/O

37

2LEBA

25

1A8-I/O

7

1B8-I/O

36

1LEBA

24

1A7-I/O

6

1B7-I/O

––

––

23

1A6-I/O

5

1B6-I/O

––

––

22

1A5-I/O

4

1B5-I/O

––

––

21

1A4-I/O

3

1B4-I/O

––

––

20

1A3-I/O

2

1B3-I/O

––

––

19

1A2-I/O

1

1B2-I/O

––

––

18

1A1-I/O

0

1B1-I/O