EFFICIENT BUILT-IN MEMORY CHECK METHOD
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-19
This circuit describes the use of a software/hard- ware accessible memory check circuit that can be used to verify program memory integrity prior to critical operations. The use of the existing Jump-to- Subroutine (JSR) instruction with a special address trap starts the checking process. The checking process passes the contents of the program memory followed by its CRC into a CRC circuit yielding a constant answer which can be easily checked by a simple hardware comparator. The checking process ends by invoking a Return-from-Subroutine (RTS) instruction that returns control to the main program. All of these elements result in an efficient and low cost solution.