Questions about DMI register op busy

[zhangdujiao]

When reading the DMI register (scanning in a value with op==0 to shift out data in the DMI register), if the previous read/write operation to DM has not been completed, will it cause op to busy in capture-dr? Does it mean that as long as the previous read/write operation to DM is not completed, the op will be 3 in capture-dr, regardless of the op of the value that will be scan in DMI register?

[pdonahue-ventana]

Yes and yes. When it does the capture, it can't possibly know what you're going to later scan into DMI.

See https://lists.riscv.org/g/tech-debug/topic/107145817#msg1697 for a recent discussion about this.

[zhangdujiao]

many thanks :)