When the application program writes a byte of data to the OCDR
register of an AVR device while being debugged, the debugger reads this value out and
displays it as IDR events in the output window as shown in the figure below. The
OCDR
register is polled at a given interval, so writing to it at a
higher frequency than the one specified for the debugger will not yield reliable results.
The data sheet of the device will explain how to check that a given value has been
read.
Note that the Output window does not have the IDR Messages
drop-down if no IDR events have been sent from the debugger.