IBM 5280 Distributed Data System - Index of

Chapter 6. Keyboard FunctionsKeyboard functions may be initiated by function keys or by program instructions.Each function is assigned an EBCD IC value between hex 00 and hex 3F. SeeAppendix C for a list of these EBCDIC values. When a keyboard function is initiated,the EBCDIC for that function is placed into the keyboard/display lOB,at relative address hex 47.Certain functions are normally processed by the 5280, but may be processed by anapplication program subroutine. Other functions are always processed by the5280, and others are always processed by an external status subroutine for externalstatus condition 1. Many functions that are processed by the 5280 must first beenabled by the application program, which must set flags in the keyboard/displaylOB.KEYBOARD FUNCTION CONTROLThe 5280 performs automatic functions and maintains certain function control.The application program must enable the automatic functions by setting flags inthe keyboard/display lOB. The keyboard function control flag bytes are maintainedby both the 5280 and the application program. The flag bytes are locatedat relative address hex BE and BF, as follows:Byte Bit Meaning if 1X'BE' 0 Keyboard is in enter mode.Keyboard is in update mode.2 Keyboard is in rerun mode. (See BF, bit 6.)3 Keyboard is in verify mode.4 An application program must not change this bit.5 An application program must not change this bit.6 Keyboard is in display mode.7 Fixed prompts are not displayed.X'BF' 0 Modified data bit is set to 0 by the 5280 when the current fieldis entered, and set to 1 by the 5280 if data is entered into thefield. When the field is exited, the 5280 DRs this bit with themodified data indicator that is assigned to the field.An application program must not change this bit.2 An application program must not change this bit.Keyboard Functions 319