參數(shù)資料
型號: SN74ABT18502PM
廠商: TEXAS INSTRUMENTS INC
元件分類: 總線收發(fā)器
英文描述: ABT SERIES, DUAL 9-BIT BOUNDARY SCAN REG TRANSCEIVER, TRUE OUTPUT, PQFP64
封裝: GREEN, PLASTIC, LQFP-64
文件頁數(shù): 5/32頁
文件大?。?/td> 578K
代理商: SN74ABT18502PM
SN74ABT18502
SCAN TEST DEVICE
WITH 18-BIT REGISTERED BUS TRANSCEIVER
SCBS753 – FEBRUARY 2002
13
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
BCR scan
The BCR is selected in the scan path. The value in the BCR remains unchanged during Capture-DR. This
operation must be performed before a boundary-run test operation to specify which test operation is to be
executed.
BCR opcodes
The BCR opcodes are decoded from BCR bits 2–0 as shown in Table 5. The selected test operation is performed
while the RUNT instruction is executed in the Run-Test/Idle state. The following descriptions detail the operation
of each BCR instruction and illustrate the associated PSA and PRPG algorithms.
Table 5. BCR Opcodes
BINARY CODE
BIT 2
→ BIT 0
MSB
→ LSB
DESCRIPTION
X00
Sample inputs/toggle outputs (TOPSIP)
X01
Pseudorandom pattern generation/36-bit mode (PRPG)
X10
Parallel signature analysis/36-bit mode (PSA)
011
Simultaneous PSA and PRPG/18-bit mode (PSA/PRPG)
111
Simultaneous PSA and binary count up/18-bit mode (PSA/COUNT)
In general, while the control-input BSCs (bits 83–72) are not included in the toggle, PSA, PRPG, or COUNT
algorithms, the output-enable BSCs (bits 83– 80 of the BSR) control the drive state (active or high impedance)
of the selected device output pins. These BCR instructions are only valid when both bytes of the device are
operating in one direction of data flow (that is 1OEAB
≠ 1OEBA and 2OEAB ≠ 2OEBA) and in the same direction
of data flow (that is 1OEAB
= 2OEAB and 1OEBA = 2OEBA). Otherwise, the bypass instruction is operated.
PSA input masking
Bits 20–3 of the BCR are used to specify device input pins to be masked from PSA operations. Bit 20 selects
masking for device input pin 2A9 during A-to-B data flow or for device input pin 2B9 during B-to-A data flow.
Bit 3 selects masking for device input pins 1A1 or 1B1 during A-to-B or B-to-A data flow, respectively. Bits
intermediate to 20 and 3 mask corresponding device input pins in order from most significant to least significant,
as indicated in Table 2. When the mask bit that corresponds to a particular device input has a logic-1 value, the
device input pin is masked from any PSA operation, meaning that the state of the device input pin is ignored
and has no effect on the generated signature. Otherwise, when a mask bit has a logic 0 value, the corresponding
device input is not masked from the PSA operation.
sample inputs/toggle outputs (TOPSIP)
Data appearing at the selected device input pins is captured in the shift-register elements of the selected BSCs
on each rising edge of TCK. This data is updated in the shadow latches of the selected input BSCs and applied
to the inputs of the normal on-chip logic. Data in the shift-register elements of the selected output BSCs is
toggled on each rising edge of TCK, updated in the shadow latches, and applied to the associated device output
pins on each falling edge of TCK.
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