Hi,

We use the Philips P89C664 microcontroller in several products. We are experiencing startup problems on some boards. The normal firmware program does not run and we see activity on PSEN starting approx 2.4ms after RESET is negated. This suggests the device is running from external program memory. However, the EA pin is strapped to VCC so the device should run from internal Flash. The entire program address space is taken with the internal Flash, so even if we have a bad jump or call in the firmware, we should stay within the internal Flash and not go to external program memory. The problem is infrequent; it happens perhaps one time in ten power-ons.

Has anyone experienced this before? If so, what was the cause and more importantly what was the cure?

Regards,
Paul Griffith