Method and apparatus of program patching in a data processing system.

摘要

A single-chip microcomputer device contains on-chip program storage in a read-only memory (17), and this program may be corrected or uptaded by patching. The ROM addresses are applied to an off-chip memory device (44) containing one bit for each potential ROM address, and each bit is set to mark the beginning address of code to be patched; an interrupt is signalled when one of these set bits is accessed by an address occurring during operation of the microcomputer. The interrupt causes the processor to branch to an off-chip program memory (40) to insert the patch code. The patch ends in a branch back to the on-chip ROM.