Equipment Determination; No Registers - Sanyo MBC-550 Series User Manual

Interrupt 11
Equipment Determination
This routine attempts to determine what optional
devices are attached to the system.
Input
No registers
The equip flag variable is set during the power on
diagnostics using the following hardware assump­
tions:
Port 60 = Low order byte of equipment
Port 3FA = Interrupt ID register of 8250
Bits 7-3 are always 0
Port 378 = Output port of printer — 8255 port that
can be read as well as written
Output
(AX) is set, bit significant, to indicate attached
I/O
Bit 15,14 = Number of printers attached
Bit 13 Not used
Bit 12 = Game I/O attached
Bit 11,10,9 = Number of RS232 cards attached
Bit 8 Unused
Bit 7,6 = Number of diskette drives
00 = 1, 01 = 2, 10 = 3, 11 = 4 only if Bit 0 = 1
Bit 5,4 = INITIAL VIDEO MODE
00 - Unused
10 - 80X25 BW using color card
Bit 3,2 = Planar RAM size (00=16K,01 =32K,10=48K,11
=64K)
Bit 1 Not used
Bit 0 = IPL from diskette
that there are diskette drives on the
system
No other registers affected
this bit indicates
5-26