We are currently trying to migrate a design from the ST90R to the ST90T (for supply reasons). We have been successful in reconfiguring the start vector in the ST90T to allow us to run from external ROM using the code developed for the ST90R. Unfortunately, at some point, the processor goes into the weeds, jumping to a routine for which there is no call. Fortunately, this is an IRQ routine that does nothing, so we can easily trace it with a logic analyzer. Unfortunately, the processor then goes through the sequence for a hard reset and jumps back to the start vector. So, essentially, the code is in a loop where it powers up, goes through several routines (including jumps to other code banks), jumps to an invalid routine, and then resets itself to do the same thing again. We have been spinning our wheels trying different approaches but cannot affect a change. At this point, we could use a consultant if someone with experience with this processor might be available.
