IBM 5280 Distributed Data System - Index of

Chapter 5. Diagnostic AidsDiagnostic aids include the display/alter function and the dump and trace functions.In addition, several instructions are intended for diagnostic use. See Chapter 4under Device Control (DEVCTL), opcode 3D, and under Keyboard Operations(KEYOP), opcode C7 for the following operations:KeyboardOperation121F202122DescriptionAllocate keyboard/display storageDevice control readDevice control writeKeyboard/display external register readKeyboard/display external register writeDISPLA Y / AL TE R FUNCTIONThe display/alter function is a diagnostic tool that allows you to examine and alterthe contents of main storage or keyboard/display storage, move the contents ofmain storage to keyboard/display storage and move the contents of keyboard/display storage to main storage.You can use only keyboard 0 (the keyboard attached to partition 0) to executedisplay/alter functions; however, during power-on checkout, you can start display/alter from any keyboard. If you do start display/alter during power-on checkout,power-on checkout and IP L do not continue when you terminate display/alter.To use the display/alter functions, the keyboard/display MPU must be operational.While you are using display/alter, no other keyboard/display operations can beperformed. Thus, you will hold up the rest of the system while using display/alter.Keyboard/display storage for keyboard 0 must be allocated to addresses FEOOthrough FFFF. Normally, keyboard/display storage is allocated by the configurationutility.Other system conditions during display/alter functions are as follows:• Magnetic stripe reader and elapsed time counter functions are not operational.• Parity errors in main storage and keyboard/display storage are not detected.• Status line data is removed from the secondary display of a dual display station.Diagnostic Aids 303