ARM Technical Support Knowledge Articles

Can give me some information about COMMTX signal and on its active level ?

Applies to: ARM11 processors

Answer

COMMTX and COMMRX are a pair of core outputs which may be connected to the interrtupt controller 
to signal the status of the debug communications channel.

Refer to the DCC in the TRM debug chapter:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0301f/Cegchcah.html

COMMTX indicates there is data in the wDTR to be read by the debugger. COMMTX will be active 
(low) when wDTRFullflag=1. At reset, COMMTX is inactive (high).

COMMRX indicates the rDTR is empty and ready to receive data from the debugger. COMMRX will be 
active (low) when rDTRFullflag=0. At reset, COMMRX is active (low).

COMMRX/COMMTX are used when the debug communications channel is interrupt driven. It is also 
possible to implement polling of the DCC and then the COMMRX/TX outputs are unused.

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