參數(shù)資料
型號(hào): SN54ABT8245JT
廠商: Texas Instruments, Inc.
英文描述: SCAN TEST DEVICES WITH OCTAL BUS TRANSCEIVERS
中文描述: 掃描測(cè)試設(shè)備與八進(jìn)制總線收發(fā)器
文件頁(yè)數(shù): 8/25頁(yè)
文件大?。?/td> 364K
代理商: SN54ABT8245JT
SN54ABT8245, SN74ABT8245
SCAN TEST DEVICES
WITH OCTAL BUS TRANSCEIVERS
SCBS124D – AUGUST 1992 – REVISED DECEMBER 1996
8
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
register overview
With the exception of the bypass register, any test register can be thought of as a serial-shift register with a
shadow latch on each bit. The bypass register differs in that it contains only a shift register. During the
appropriate capture state (Capture-IR for instruction register, Capture-DR for data registers), the shift register
can be parallel loaded from a source specified by the current instruction. During the appropriate shift state
(Shift-IR or Shift-DR), the contents of the shift register are shifted out from TDO while new contents are shifted
in at TDI. During the appropriate update state (Update-IR or Update-DR), the shadow latches are updated from
the shift register.
instruction register description
The instruction register (IR) is eight bits long and tells the device what instruction is to be executed. Information
contained in the instruction includes the mode of operation (either normal mode, in which the device performs
its normal logic function, or test mode, in which the normal logic function is inhibited or altered), the test operation
to be performed, which of the three data registers is to be selected for inclusion in the scan path during
data-register scans, and the source of data to be captured into the selected data register during Capture-DR.
Table 3 lists the instructions supported by the ’ABT8245. The even-parity feature specified for SCOPE
devices
is supported in this device. Bit 7 of the instruction opcode is the parity bit. Any instructions that are defined for
SCOPE
devices but are not supported by this device default to BYPASS.
During Capture-IR, the IR captures the binary value 10000001. As an instruction is shifted in, this value is shifted
out via TDO and can be inspected as verification that the IR is in the scan path. During Update-IR, the value
that has been shifted into the IR is loaded into shadow latches. At this time, the current instruction is updated,
and any specified mode change takes effect. At power up or in the Test-Logic-Reset state, the IR is reset to the
binary value 11111111, which selects the BYPASS instruction.
The IR order of scan is shown in Figure 2.
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
TDO
TDI
Bit 7
Parity
(MSB)
Bit 0
(LSB)
Figure 2. Instruction Register Order of Scan
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