On board non-volatile memory programming

Abstract

A digital system is disclosed for programming a non-volatile memory, such as a programmable read only memory (PROM), while it is in situ in the operating system of which it forms a part. The digital system includes a read/write (R/W) memory and a non-volatile memory which communicate with one another through a two-way data communication bus. Data, address, and circuit select signals are provided to the R/W memory to enter information therein. Upon completion of entry of the data (e.g., a control program) into R/W memory, timing circuitry provides selective signals, such as circuit select, program pulse and program voltage signals to the non-volatile PROM memory and the data or control program is transferred to the PROM memory without removing the PROM from the system. Additional circuitry allows this data or control program stored in the PROM memory to be transferred back to R/W memory, modified and then transferred back to PROM memory. Verify circuitry is included to compare the R/W memory data with the PROM memory data for differences to indicate programming errors and also to check the PROM to ensure, prior to programming, that it is completely erased and ready for programming.