The present application relates to the field of
integrated circuit test and embedded
chip debugging technology, and particularly relates to a JTAG communication implementation method without IR decoding, comprising the following steps: S1, receiving a reset
signal to make a JTAG state
machine enter a Test-Logic-Reset state; S2, detecting a TMS pin level in the Test-Logic-Reset state, if the TMS pin level is low,
jumping to a Run-Test / Idle state, otherwise maintaining the current state; S3, counting a TCK
clock rising edge in the Run-Test / Idle state, the count value is recorded as C, and
jumping to a SelectDR-Scan state when the TMS is high; S4, in the SelectDR-Scan state, if the TMS is high, returning to the Test-Logic-Reset, if the TMS is low, entering a Capture-DR state. The present application discards all IR related states in the standard JTAG protocol, simplifies the original 16 state
machine into 9 effective states containing only the DR path, and does not need to perform scanning and decoding operations of the
instruction register in the communication process, directly determines the access target by counting the TCK
clock, which removes the IR decoding circuit on the one hand, and saves multiple IR state periods in the traditional JTAG on the other hand.