I check the HP200LX ROM BIOS.
Location FFFF0h contains a "jump" instruction.
F000:FFF0 JMP F000:E05B
Here's the real BIOS startup program.
F000:E05B MOV SP,CS
F000:E05D MOV SS,SP
F000:E05F MOV SP,E065
F000:E062 JMP E810
Then jump to F000:E810.
F000:E810 CLI
F000:E811 MOV AL,18
F000:E813 OUT 22,AL
F000:E815 IN AL,23
F000:E817 AND AL,02
F000:E819 OUT 23,AL
F000:E81B XOR AH,AH
F000:E81D MOV AL,19
F000:E81F OUT 22,AX
F000:E821 MOV AL,54
F000:E823 OUT 22,AX
F000:E825 MOV AL,59
F000:E827 OUT 22,AX
F000:E829 RET
I know the I/O port No.00-0F is DMA controller and the port No.20-21 is
interrupt controller. But I don't know how to use the port No22 and 23.
Anyone know the I/O port No.22,23 meaning on the HP200LX? Thanks for any help.
Tadayoshi Kubo
