Apparatus for repairing faulty program segments in embedded

Abstract

A program repairing apparatus is provided for use on an embedded microprocessor system to repair any faulty program segments that are stored in a permanent data storage unit, such as a mask ROM (read-only memory) incorporated in the embedded microprocessor system. These faulty program segments are repaired by using a number of repair program segments loaded in a reloadable storage unit, such as a RAM (random-access memory) unit that represent the correct versions of the faulty program segments. With this program repairing apparatus, the programs stored in the ROM unit can be repaired without carrying out a mask programming process. In this program repairing apparatus, the starting addresses of the faulty program segments in the ROM unit are registered in a faulty-segment address table and the starting addresses of the repair program segments in the RAM unit are registered in a repair-segment address table. When the current access address is the starting address of any one of the faulty program segments, a comparison circuit and a multiplexer are used in conjunction to change the access address to the starting address of the corresponding repair program segment in the RAM unit. This allows the embedded microprocessor system to execute the program codes in the repair program segment instead of the faulty program codes in the faulty program segment.