David Michael Snider

US Patent:

45424535, Sep 17, 1985

Filed:

Feb 19, 1982

Appl. No.:

6/350513

Inventors:

Michael J. Patrick - Houston TX
David M. Snider - Cary NC

Assignee:

Texas Instruments Incorporated - Dallas TX
IBM Corp. - Dallas TX

International Classification:

G06F 900
G06F 700

US Classification:

364200

Abstract:

A single-chip microcomputer device contains on-chip program storage in a read-only memory (ROM), and this program may be corrected or updated by patching. The ROM addresses are applied to an off-chip memory device 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 to insert the patch code. The patch ends in a branch back to the on-chip ROM.