8.7.3. Instruction register

This register changes the current TAP instruction. The register is 4 bits in length

Operating mode

When in the SHIFT-IR state, the instruction register is selected as the serial path between TDI and TDO.

During the CAPTURE-IR state, the value 0001 binary is loaded into this register. This is shifted out during SHIFT-IR least significant bit (lsb) first, while a new instruction is shifted in (lsb first).

During the UPDATE-IR state, the value in the instruction register becomes the current instruction.

On reset, IDCODE becomes the current instruction.

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