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DIGITAL-LOGIC AG MSB900/L Detailed Technical Manual V1.0
39
I/O Map
Continued…
I/O Addr.
Function Size
R/W Comment
3F1h
Floppy Status R B 8bit RO First Floppy.
3F2h
Floppy Digital Out 8bit Shw@
First Floppy.
3F3h
No Specific Usage 8bit ---
3F4h
Floppy Cntrl Status 8bit RO First Floppy.
3F5h Floppy Data 8bit Yes First Floppy.
3F6h
No Specific Usage 8bit ---
3F7h
Floppy Conf Reg 8bit Shw$
First Floppy.
3F8h-3FFh
UART/IR - COM1 8bit ---
MSR bit enables/disables into I/O
3FFh space. (UART1 MSR
51400014h[18:16], UART2 MSR
51400014h[22:20]). Defaults to
LPC.
480h
No Specific Usage 8bit WO Write LPC and DMA. Read only DMA.
481h
DMA Channel 2 High Page 8bit Rec
Upper addr bits [31:24]. Write LPC and DMA.
Read only DMA.
482h DMA Channel 3 High Page
483h DMA Channel 1 High Page
484h-486h
No Specific Usage 8bit WO Write LPC and DMA. Read only DMA.
487h
DMA Channel 0 High Page 8bit Rec
Upper addr bits [31:24]. Write LPC and DMA.
Read only DMA.
489h
DMA Channel 6 High Page 8bit Rec
Upper addr bits [31:24]. Write LPC and DMA.
Read only DMA.
48Ah DMA Channel 7 High Page
48Bh DMA Channel 5 High Page
48Ch-48Eh
No Specific Usage 8bit WO Write LPC and DMA. Read only DMA.
48Fh
DMA Channel 4 High Page 8bit Rec
Upper addr bits [31:24]. Write LPC and DMA.
Read only DMA.
490h-4CFh
No Specific Usage --- ---
4D0h
PIC Level/Edge 8bit Yes IRQ0-IRQ 7.
4D1h
PIC Level/Edge 8bit Yes IRQ8-IRQ15.
4D2h-4FFh
No Specific Usage --- ---
Note 1: The Diverse Device Snoops writes to this port and maintains the MSB as NMI enabled. When low,
NMI is enabled. When high, NMI is disabled. This bit defaults high. Reads of this port return bits
[6:0] from the on-chip or off-chip target, while Bit 7 is returned from the “maintained” value.