Datasheet

SN54ABT8543, SN74ABT8543
SCAN TEST DEVICES WITH
OCTAL REGISTERED BUS TRANSCEIVERS
SCBS120E – AUGUST 1991 – REVISED JULY 1996
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Table 1. Boundary-Scan Register Configuration
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
BSR BIT
NUMBER
DEVICE
SIGNAL
39 OEB 31 A8-I 23 A8-O 15 B8-I 7 B8-O
38 OEA 30 A7-I 22 A7-O 14 B7-I 6 B7-O
37
OEAB
29 A6-I 21 A6-O 13 B6-I 5 B6-O
36
OEBA
28 A5-I 20 A5-O 12 B5-I 4 B5-O
35
LEAB
27 A4-I 19 A4-O 11 B4-I 3 B4-O
34
LEBA
26 A3-I 18 A3-O 10 B3-I 2 B3-O
33
CEAB
25 A2-I 17 A2-O 9 B2-I 1 B2-O
32
CEBA
24 A1-I 16 A1-O 8 B1-I 0 B1-O
boundary-control register
The boundary-control register (BCR) is 11 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, PSA with input masking, and binary count up (COUNT). Table 4 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 00000000010, which selects the PSA test operation with no input masking.
The BCR order of scan is from TDI through bits 10–0 to TDO. Table 2 shows the BCR bits and their associated
test control signals.
Table 2. Boundary-Control Register Configuration
BCR BIT
NUMBER
TEST
CONTROL
SIGNAL
BCR BIT
NUMBER
TEST
CONTROL
SIGNAL
BCR BIT
NUMBER
TEST
CONTROL
SIGNAL
10 MASK8 6 MASK4 2 OPCODE2
9 MASK7 5 MASK3 1 OPCODE1
8 MASK6 4 MASK2 0 OPCODE0
7 MASK5 3 MASK1 –– ––
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 shown in Figure 3.
Bit 0
TDOTDI
Figure 3. Bypass Register Order of Scan