Datasheet

SN54BCT8374A, SN74BCT8374A
SCAN TEST DEVICES
WITH OCTAL D-TYPE EDGE-TRIGGERED FLIP-FLOPS
SCBS045E − JUNE 1990 − REVISED JULY 1996
9
POST OFFICE BOX 655303 DALLAS, TEXAS 75265
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251−1443
data register description
boundary-scan register
The boundary-scan register (BSR) is 18 bits long. It contains one boundary-scan cell (BSC) for each
normal-function input pin and one BSC for each normal-function output pin. The BSR is used to 1) store test
data that is to be applied internally to the inputs of the normal on-chip logic and/or externally to the device output
terminals, 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 terminals.
The source of data to be captured into the BSR during Capture-DR is determined by the current instruction. The
contents of the BSR may change during Run-Test/Idle as determined by the current instruction. The contents
of the BSR are not changed in Test-Logic-Reset.
The BSR order of scan is from TDI through bits 17−0 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
17 CLK 15 1D 7 1Q
16 OE 14 2D 6 2Q
13 3D 5 3Q
12 4D 4 4Q
11 5D 3 5Q
10 6D 2 6Q
9 7D 1 7Q
8 8D 0 8Q
boundary-control register
The boundary-control register (BCR) is two 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 and PSA. Table 3 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 10, which selects the PSA test operation. The BCR order of scan is shown in Figure 3.
Bit 1
(MSB)
TDOTDI
Bit 0
(LSB)
Figure 3. Boundary-Control Register Order of Scan