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Copyright 1991 David Jurgens |
EBDA - Extended BIOS Data Area EBDA (PS/2)
Offset Size Description
00 word number of bytes allocated to EBDA in Kbytes
01-21 21bytes reserved
22 dword device driver far call pointer
26 byte pointing device flag (1st byte, see below)
27 byte pointing device flag (2nd byte, see below)
28-2F 8 bytes reserved
Pointing Device Flag Byte 1
│7│6│5│4│3│2│1│0│ Offset 26
│ │ │ │ │ └─┴─┴─── index count
│ │ │ │ └──────── reserved (0)
│ │ │ └───────── error
│ │ └────────── acknowledge
│ └─────────── resend
└──────────── command in progress
Pointing Device Flag Byte 2
│7│6│5│4│3│2│1│0│ Offset 27
│ │ │ │ │ └─┴─┴─── package size
│ └─┴─┴─┴──────── reserved
└─────────────── device driver far call flag
- EBDA is located in highest memory just under 640K on PS/2
- word at BIOS Data Area 40:0E is segment address of EBDA
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EBDA |
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