Concurrent Operation of the IBM Personal Computer Display Station Adapter and Disk File
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19
The IBM Personal Computer (PC) Display Station Adapter and the IBM Personal Computer Disk File use the same Direct Memory Access (DMA) channel and therefore cannot be used concurrently. If the display station adapter is inoperative for more than 100 msec., the IBM 5520 System will time-out the terminal. A protocol is established between the IBM Personal Computer 5253 Emulation program using the IBM Personal Computer Display Station Adapter and the IBM 5520 administration system. The protocol is as follows: 1. The application processor requests the Hard File Access. 2. The Disk/Diskette Access Program (DAP) requests 5520 system session to be suspended. 3. The Emulator program posts the requests on the next unhooked pole signal from the 5520. 4. The IBM 5520 completes all current terminal operations. 5.