Compaq MSB900 - Manual (Page 36)

DIGITAL-LOGIC AG MSB900/L Detailed Technical Manual V1.0
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5.9.2. System I/O map
The following table details the legacy I/O range for 000h through 4FFh. Each I/O location has a read/write
(R/W) capability.
Note the following abbreviations:
--- Unknown or can not be determined.
Yes Read and write the register at the indicated location. No shadow required.
WO Write only. Value written can not be read back. Reads do not contain any useful information.
RO Read only. Writes have no effect.
Shw
The value written to the register can not be read back via the same I/O location. Read back is
accomplished via a “Shadow” register located in MSR space.
Shw@ Reads of the location return a constant or meaningless value.
Shw$ Reads of the location return a status or some other meaningful information
Rec
Writes to the location are “recorded” and written to the LPC. Reads to the location return the re-
corded value. The LPC is not read.
I/O Map
I/O Addr. Function Size R/W Comment
000h Slave DMA Address - Channel 0 8bit Yes 16bit values in two transfers.
001h Slave DMA Counter - Channel 0 8bit Yes 16bit values in two transfers.
002h Slave DMA Address - Channel 1 8bit Yes 16bit values in two transfers.
003h Slave DMA Counter - Channel 1 8bit Yes 16bit values in two transfers.
004h Slave DMA Address - Channel 2 8bit Yes 16bit values in two transfers.
005h Slave DMA Counter - Channel 2 8bit Yes 16bit values in two transfers.
006h Slave DMA Address - Channel 3 8bit Yes 16bit values in two transfers.
007h Slave DMA Counter - Channel 3 8bit Yes 16bit values in two transfers.
008h Slave DMA Command/Status - Channels [3:0] 8bit Shw$
009h Slave DMA Request - Channels [3:0] 8bit WO Reads return value B2h.
00Ah Slave DMA Mask - Channels [3:0] 8bit Shw@ Reads return value B2h.
00Bh Slave DMA Mode - Channels [3:0] 8bit Shw@ Reads return value B2h.
00Ch Slave DMA Clear Pointer - Channels [3:0] 8bit WO Reads return value B2h.
00Dh Slave DMA Reset - Channels [3:0] 8bit WO Reads return value B2h.
00Eh Slave DMA Reset Mask - Channels [3:0] 8bit Shw@ Reads return value B2h.
00Fh Slave DMA General Mask - Channels [3:0] 8bit Shw@ Reads return value B2h.
010h-01Fh No Specific Usage --- ---
020h PIC Master - Command/Status 8bit Shw$
021h PIC Master - Command/Status 8bit Shw$
022h-03Fh No Specific Usage --- ---
040h PIT – System Timer 8bit Shw$
041h PIT – Refresh Timer 8bit Shw$
042h PIT – Speaker Timer 8bit Shw$
043h PIT – Control 8bit Shw$
044h-05Fh No Specific Usage --- ---
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