SN54LVT18502

3.3-V ABT SCAN TEST DEVICE

WITH 18-BIT UNIVERSAL BUS TRANSCEIVERS

SCBS669 – JULY 1996

15

POST OFFICE BOX 655303

pseudo-random pattern generation (PRPG)

A pseudo-random pattern is generated in the shift-register elements of the selected BSCs on each rising edge

of TCK, updated in the shadow latches, and applied to the associated device output-mode I/O pins on each

falling edge of TCK. Figures 5 and 6 show the 36-bit linear-feedback shift-register algorithms 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 does not produce additional patterns.

=

1B8-I/O

1B7-I/O

1B6-I/O

1B5-I/O

1B4-I/O

1B3-I/O

1B2-I/O

1B1-I/O

1B9-I/O

1A7-I/O

1A6-I/O

1A5-I/O

1A4-I/O

1A3-I/O

1A2-I/O

1A1-I/O

1A8-I/O

1A9-I/O

2A7-I/O

2A6-I/O

2A5-I/O

2A4-I/O

2A3-I/O

2A2-I/O

2A1-I/O

2A8-I/O

2A9-I/O

2B8-I/O

2B7-I/O

2B6-I/O

2B5-I/O

2B4-I/O

2B3-I/O

2B2-I/O

2B1-I/O

2B9-I/O

Figure 5. 36-Bit PRPG Configuration (1OEAB = 2OEAB = 0, 1OEBA = 2OEBA = 1)