Datasheet

211
6120F–ATARM–03-Oct-06
AT91SAM7X512/256/128 Preliminary
Figure 26-12. Test Modes
26.4.6 Debug Communication Channel Support
The Debug Unit handles the signals COMMRX and COMMTX that come from the Debug Com-
munication Channel of the ARM Processor and are driven by the In-circuit Emulator.
The Debug Communication Channel contains two registers that are accessible through the ICE
Breaker on the JTAG side and through the coprocessor 0 on the ARM Processor side.
As a reminder, the following instructions are used to read and write the Debug Communication
Channel:
MRC p14, 0, Rd, c1, c0, 0
Returns the debug communication data read register into Rd
MCR p14, 0, Rd, c1, c0, 0
Writes the value in Rd to the debug communication data write register.
The bits COMMRX and COMMTX, which indicate, respectively, that the read register has been
written by the debugger but not yet read by the processor, and that the write register has been
written by the processor and not yet read by the debugger, are wired on the two highest bits of
the status register DBGU_SR. These bits can generate an interrupt. This feature permits han-
dling under interrupt a debug link between a debug monitor running on the target system and a
debugger.
Receiver
Transmitter
Disabled
RXD
TXD
Receiver
Transmitter
Disabled
RXD
TXD
V
DD
Disabled
Receiver
Transmitter
Disabled
RXD
TXD
Disabled
Automatic Echo
Local Loopback
Remote Loopback
V
DD