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Compaq Deskpro EX and Deskpro EXS Series of Personal Computers 6-3
6.1.4 ICH Fixed I/O Registers
Port Register Name
00h, 02h, 04h, 06h Channel 0, 1, 2, 3 DMA Base & Current Address Regsiter
C0h, C4h, C8h, CCh Channel 4, 5, 6, 7 DMA Base & Current Address Register
01h, 03h, 05h, 07h Channel 0, 1, 2, 3 DMA Base & Current Count Register
C2h, C6h, Cah, CEh Channel 4, 5, 6, 7 DMA Base & Current Count Register
10h-1Fh
Aliased at 00h-0Fh
20h Master PIC ICW1 Init. Cmd Word 1 Register
Master PIC OCW2 Op Ctrl Word 2 Register
Master PIC OCW3 Op Ctrl Word 3 Register
21h Master PIC ICW2 Init. Cmd Word 1 Register
Master PIC ICW3 Init. Cmd Word 1 Register
Master PIC ICW4 Init. Cmd Word 1 Register
Master PIC OCW1 Op Ctrl Word 3 Register
24h-25h, 28-29h,
2Ch-2Dh, 30h-31h,
34h-35h, 38h-39h,
3Ch-3Dh
Aliased at 20h-21h
40h Counter 0 Interval Time Status Byte Format
Counter 0 Counter Access Port Register
41h Counter 1 Interval Time Status Byte Format
Counter 1 Counter Access Port Register
42h Counter 2 Interval Time Status Byte Format
Counter 2 Counter Access Port Register
43h Timer Control Word Register
Timer Control Word Register Read Back
Counter Latch Command
50h-53h
Aliased at 40h-43h
61h NMI Status and Control Register
70h NMI Enable Register
Real-Time Clock (Standard RAM) Index Register
71h Real-Time Clock (Standard RAM) Target Register
72h Extended RAM Index Register
73h Extended RAM Target Register
74h-75h
Aliased at 70h-71h
76h-77h
Aliased at 72h-73h or 70h-71h
81h, 82h, 83h Channel 2, 3, 1 DMA Memory Low Page Register
84h-86h, 88h Reserved Page Registers
89h, 8Ah, 8Bh Channel 6, 7, 5 DMA Memory Low Page Register
8CH-8Eh Reserved Page Registers
8Fh Refresh Low Page Register
91h-9Fh
(except 92h)
Aliased at 81h-8Fh
92h Fast A20 and INIT Register
continued