參數(shù)資料
型號(hào): SN54BCT8240AFK
廠商: Texas Instruments, Inc.
英文描述: SCAN TEST DEVICES WITH OCTAL INVERTING BUFFERS
中文描述: 掃描測(cè)試設(shè)備與八進(jìn)制反向緩沖器
文件頁(yè)數(shù): 8/26頁(yè)
文件大?。?/td> 473K
代理商: SN54BCT8240AFK
SN54BCT8240A, SN74BCT8240A
SCAN TEST DEVICES
WITH OCTAL INVERTING BUFFERS
SCBS067E – FEBRUARY 1990 – REVISED DECEMBER 1996
8
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
register overview
With the exception of the bypass register, any test register may 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
may 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 2 lists the instructions supported by the ’BCT8240A. The even-parity feature specified for SCOPE
devices is not supported in this device. Bit 7 of the instruction opcode is a don’t-care 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
(MSB)
Don’t
Care
Bit 0
(LSB)
Figure 2. Instruction Register Order of Scan
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 1) to 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.
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