2.11.3.4 Instruction Register (IR)

The IR has five bits (IR4 to IR0). At the TRST state, IR is reset to IDCODE. Each time when IR is selected, it goes through “select IR-Scan,” “Capture-IR,” “Shift-IR,” all the way through “Update-IR.” When there is no test error, the first five data bits coming out of TDO during the “Shift-IR” will be “10111”. If a test error occurs, the last three bits will contain one to three zeroes corresponding to negatively asserted signals: “TDO_ERRORB,” “PROBA_ERRORB,” and “PROBB_ERRORB.” The error(s) will be erased when the TAP is at the “Update-IR” or the TRST state. When in user mode start-up sequence, if the micro-probe has not been used, the “PROBA_ERRORB” is used as a “Power-up done successfully” flag.