Multiple patches to on-chip ROM in a processor with a multilevel memory system without affecting performance

摘要

A programmable address decoder is common to the on-chip ROM and on-chip RAM. The programmable address decoder conditionally routes accesses to portions of the ROM to the RAM. The ROM address space is mapped to RAM via a set of configuration registers. This permits patched ROM program code and data table to be stored in on-chip RAM. The patched code and configuration data is stored in an off-chip non-volatile memory. This patch code and the configuration to use is loaded into the RAM and configuration registers on system bootstrap procedure.