There are several memory locations in low core that are mapped to specific CPU functions. \u00a0These memory locations provide a direct way for the program to communicate with the CPU. \u00a0We will reserve the first 1k of memory for CPU usage. \u00a0Here are some of the memory mapped locations we will need to use:<\/p>\n
RSTNPSW DS D RESTART NEW PSW\r\nRSTOPSW DS D RESTART OLD PSW\r\n DS F\r\n DS F\r\nEXTOPSW DS D EXTERNAL OLD PSW\r\nSVCOPSW DS D SVC OLD PSW\r\nPGMOPSW DS D PROGRAM OLD PSW\r\nMCKOPSW DS D MACHINE CHECK OLD PSW\r\nIO$OPSW DS D I\/O OLD PSW\r\nCSW DS D CHANNEL STATUS WORD\r\nCAW DS F CHANNEL ADDRESS WORD\r\n DS F\r\nITIMER DS F INTERVAL TIMER\r\n DS F\r\nEXTNPSW DS D EXTERNAL NEW PSW\r\nSVCNPSW DS D SVC NEW PSW\r\nPGMNPSW DS D PROGRAM NEW PSW\r\nMCKNPSW DS D MACHINE CHECK NEW PSW\r\nIO$NPSW DS D I\/O NEW PSW<\/pre>\nI have created a macro (@LOWCORE) to map these memory locations. \u00a0We will use the two words following the Restart Old PSW as pointers to control blocks. \u00a0This will allow the control blocks to be easily located since they are anchored at a fixed location.<\/p>\n
[Next – TXXNUC00<\/a>]<\/p>\n","protected":false},"excerpt":{"rendered":"
There are several memory locations in low core that are mapped to specific CPU functions. \u00a0These memory locations provide a direct way for the program to communicate with the CPU. \u00a0We will reserve the first 1k of memory for CPU … Continue reading