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    參數(shù)資料
    型號: SN54ABT182502A
    廠商: Texas Instruments, Inc.
    英文描述: Scan Test Devices With 18-Bit Universal Bus Transceivers(掃描測試裝置(帶18位通用總線收發(fā)器))
    中文描述: 掃描測試設(shè)備與18位通用總線收發(fā)器(掃描測試裝置(帶18位通用總線收發(fā)器))
    文件頁數(shù): 9/35頁
    文件大?。?/td> 738K
    代理商: SN54ABT182502A
    SN54ABT18502A, SN54ABT182502A, SN74ABT18502A, SN74ABT182502A
    SCAN TEST DEVICES WITH
    18-BIT UNIVERSAL BUS TRANSCEIVERS
    SCBS488 – AUGUST 1994
    9
    POST OFFICE BOX 655303
    DALLAS, TEXAS 75265
    register overview
    With the exception of the bypass and device identification registers, any test register can be thought of as a serial
    shift register with a shadow latch on each bit. The bypass and device identification registers differ in that they
    contain 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 four 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
    ABT18502A and
    ABT182502A. 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 10000001, which selects the IDCODE instruction.
    The IR order of scan is illustrated 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
    P
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