I read carefully the Release Notes of CW V10.3 and noticed something in the bug fixes for HCS08:
Enable P&E run control device to read 9S08PT memory while the device is
running
I thought that bug wasn't really fixed, to corroborate I tried reading variables using FreeMaster and got same results, random numbers and occasionally a correct value, so yes, it might be a silicon bug.
The microcontroller soldered on the prototype I'm working on has a 4N40C Mask (silicon revision?) and I could only find this:
http://cache.freescale.com/files/32bit/doc/errata/MSE9S08PT60_4N40C.pdf
Which says nothing about memory access while running.
I think this is the down side of working with the latest uc families :smileysad: However, it's not so critical as I'm about to finish the display driver and could use that as a live variable view workaround.