ACT apricot - Page 277

CONTROL DEVICE
When the routine is called as an absolute jump to the
location 0000:0600H, the first three items above have to be
pushed (as words) onto the stack. The routine can also be
accessed
through INTERRUPT OFCH, which machine
language programmers will find more convienient. In this
case, the parameters are passed in the registers like so:
BX - Device number (DEV)
CX-Command(COM)
DX - Data (DAT)
And the status is returned as:
AX - Status/Data (RET)
All the 8086 registers & the flags are saved
The three items of data are all numeric values. The device
number is one of the following:
ASCII
HEX DEC DEVICE NAME
1
31H
49
Screen driver
2
32H
50
Keyboard driver
3
33H 51
MicroScreen driver
4
34H 52
Serial Input/Ouput driver
5
35H 53
Parallel
Input/Output driver
6
36H
54
Mouse driver
7
37H
55
Clock driver
8
38H 56
Sound generator/driver
9
39H 57
Floppy
Disk Drivers
B
42H
66
Cache/Graphics/IBM config
The command, data and return status all vary depending
on which device is being accessed.