addr. size description ----- ------ ------------------------------------------------------------- 40:00 word COM1 port address | These addresses are zeroed out in the 40:02 word COM2 port address | OS/2 DOS Compatibility Box if any of 40:04 word COM3 port address | the OS/2 COM??.SYS drivers are loaded. 40:06 word COM4 port address | 40:08 word LPT1 port address 40:0A word LPT2 port address 40:0C word LPT3 port address 40:0E word LPT4 port address (not valid in PS/2 machines) 40:0E word PS/2 pointer to BIOS/ExtData extended Data Area at top of RAM 40:10 word Installed Equipment Flag BIOS/40/10 40:12 byte reserved (PC, AT) number of errors detected by infrared keyboard link (PCjr) POST status (Convertible) 40:13 word availible memory size in Kbytes (less display RAM in PCjr) this is the value returned by Int/12 also serves as a pointer to the Extended BIOS Data Area 40:15 word reserved 40:17 2byte keyboard Flags BIOS/40/17 40:19 byte storage for alternate keypad entry (not normally used) 40:1A word pointer to keyboard buffer head character 40:1C word pointer to keyboard buffer tail character 40:1E 32byte 16 2-byte entries for keyboard circular buffer. Int/16 40:3E byte drive seek status BIOS/40/3E 40:3F byte diskette motor status BIOS/40/3F 40:40 byte motor off counter starts at 37 and is decremented 1 by each system clock tick. motor is shut off when count = 0. 40:41 byte status of last diskette operation BIOS/40/41 40:42 7 byte Floppy controller status bytes 40:49 byte current CRT mode (hex value) BIOS/40/49 40:4A word number of columns on screen, coded as hex number of columns for example 20, 40, and 80 are 14h, 28h, and 46h 40:4C word screen buffer length in bytes (number of bytes used per screen page, varies with video mode) 40:4E word current screen buffer starting offset (active page) 40:50 8 words cursor position pages 1-8 the first byte of each word gives the column (0-19, 39, or 79) the second byte gives the row (0-24) 40:60 byte end line for cursor (normally 1) 40:61 byte start line for cursor (normally 0) 40:62 byte current video page being displayed (0-7) 40:63 word base port address of 6845 CRT controller or equivalent for active display 3B4h=mono, 3D4h=color 40:65 byte current setting of the CRT mode register 40:66 byte current palette mask setting (CGA) 40:67 5 bytes temporary storage for SS:SP during shutdown (cassette interface) 40:69 byte Disk drives installed data (Columbia PCs) (not valid on most clone computers) BIOS/40/69 40:6C word timer counter low word. See Int/1Af/00 40:6E word timer counter high word. See Int/1Af/00 40:70 byte 24 hour timer overflow 1 if timer went past midnight it is reset to 0 each time it is read by Int/1A 40:71 byte BIOS break flag (bit 7 = 1 means break key hit) 40:72 word reset flag PCjr keeps 1234h here for softboot when a cartridge is installed bits 1234h = soft reset, memory check will be bypassed 4321h = preserve memory (PS/2 other only) 5678h = system suspended (Convertible) 9ABCh = manufacturing test mode (Convertible) ABCDh = system POST loop mode (Convertible) 40:74 byte status of last hard disk operation; PCjr special disk control 40:75 byte # of hard disks attached (0-2) ; PCjr special disk control 40:76 byte HD control byte; temp holding area for 6th param table entry 40:77 byte port offset to current hd adapter ; PCjr special disk control 40:78 4 bytes timeout value for LPT1,LPT2,LPT3,LPT4 40:7C 4 bytes timeout value for COM1,COM2,COM3,COM4 (0-0FFh secs, default 1) 40:80 word pointer to start of circular keyboard buffer, default 03:1E 40:82 word pointer to end of circular keyboard buffer, default 03:3E 40:84 byte rows on the screen minus 1 (EGA only) 40:84 byte PCjr interrupt flag; timer channel 0 (used by POST) 40:85 word bytes per character (EGA only) 40:85 2 bytes (PCjr only) typamatic char to repeat 40:86 2 bytes (PCjr only) typamatic initial delay 40:87 word mode options and feature bit switches (EGA only) 40:87 byte (PCjr only) current Fn key code 40:88 byte (PCjr only) special keyboard status byte bit 7 function flag 3 typamatic (0=enable,1=disable) 6 Fn-B break 2 typamatic speed (0=slow,1=fast) 5 Fn pressed 1 extra delay bef.typamatic (0=enable) 4 Fn lock 0 write char, typamatic delay elapsed 40:89 byte PCjr, current value of 6845 reg 2 (horiz.synch) used by ctrl-alt-cursor screen positioning routine in ROM 40:8A byte PCjr CRT/CPU Page Register Image, default 3Fh 40:8B byte last diskette data rate selected 40:8C byte hard disk status returned by controller 40:8D byte hard disk error returned by controller 40:8E byte hard disk interrupt (bit 7=working int) 40:90 4 bytes media state drive 0, 1, 2, 3 40:94 2 bytes track currently seeked to drive 0, 1 40:96 byte keyboard flag byte 3 (see Int/09) 40:97 byte keyboard flag byte 2 (see Int/09) 40:98 dword segment:offset pointer to users wait flag 40:9C dword users timeout value in microseconds 40:A0 byte real time clock wait function in use bits 7 wait time elapsed and posted flag 6-1 reserved 0 Int/15f/86 (WAIT) has occurred 40:A1 byte LAN A DMA channel flags 40:A2 2 bytes status LAN A 0,1 40:A4 dword saved hard disk interrupt vector 40:A8 dword EGA pointer to table of 7 parameters. Format of table: dword pointer to 1472 byte table containing 64 video parms dword reserved dword reserved dword reserved dword reserved dword reserved dword reserved 40:B4 byte keyboard NMI control flags (Convertible) 40:B5 dword keyboard break pending flags (Convertible) 40:B9 byte port -0060 single byte queue (Convertible) 40:BA byte scan code of last key (Convertible) 40:BB byte pointer to NMI buffer head (Convertible) 40:BC byte pointer to NMI buffer tail (Convertible) 40:BD 16bytes NMI scan code buffer (Convertible) 40:CE word day counter (Convertible and after) 04:8F end of BIOS Data Area
file: /Techref/bios/dataarea.htm, 7KB, , updated: 1999/2/20 10:24, local time: 2024/12/3 21:33,
18.97.14.82:LOG IN
|
©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions? <A HREF="http://www.massmind.org/techref/bios/dataarea.htm"> Memory Map of the 000400-000500 BIOS Data Area</A> |
Did you find what you needed? |
Welcome to massmind.org! |
Welcome to www.massmind.org! |
.