I am trying to find a way to dump the rom contents of several MAB8421 microcontrollers. I know that on many 8048 MCUs, you can use the external access pin to dump the rom, but the 8421 doesn't have any external memory pin. I was wondering if there was possibly another way to dump the rom, but there is little to no documentation I could find on a process of doing so.
The MAB8421 is a version with the factory mask ROM, so while the MCU core is the same as with the ROM-less version which requires external ROM, the pins for the ROM are used internally and there is no access to these pins.
So without hacking into the chip and looking or debugging the silicon, there is no way to dump the ROM contents. Unless the software has a feature to transmit out the ROM contents somehow, but that ìs unlikely.