Terminal microcode Load/ Patch Facility
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
The functions of a cathode ray tube (CRT) terminal (not shown) are carried out as microprocessing unit (MPU) 10 executes instructions from read-only storage (ROS) control store 20. In order to accommodate features and/or patches for the microcode in control store 20, linkages or subroutine calls are placed at many suitable locations. The linkages or calls are directed to locations in random-access memory (RAM) 25. The RAM feature/patch linkage area in initialized to the subroutine return operation code whereby any later calls return to the very next ROS control store instruction.