AUD

Interface description
The interface itself is 4 data lines, and 4 control lines (reset, clock, mode, sync). Refer to the mcu datasheet for more info, both in the AUD chapter and the Electrical Characteristics -> AC Characteristics section.

Branch trace mode
In this mode, the mcu generates the clock signal (typically @ 20MHz) and shifts out 4 bits every clock, therefore specialized or very fast hardware is required to read the data. A fast enough logic analyzer can do this (at least 6 simultaneous channels at >= 80MSps).

RAM monitor mode
The AUD port accepts commands to read/write to the RAM. This mode has also been used succesfully to dump the entire ROM.

Example code
There are a few examples floating around the oldweb, some of which were collected here:
 * mirror of old ecuhacking forum examples