
Functional Description
5-58
82801AA and 82801AB Datasheet
5.12.8.1
Write Only Registers with Read Paths in Alternate Access Mode
The registers described in
Table 5-44
have read paths in alternate access mode. The access number
field in the table indicates which register will be returned per access to that port.
Table 5-44. Write Only Registers with Read Paths in Alternate Access Mode (Sheet 1 of 2)
I/O
# of
Restore Data
I/O
# of
Restore Data
Addr
Rds
Access
Data
Addr
Rds
Access
Data
00h
2
1
DMA Chan 0 base address
low byte
DMA Chan 0 base address
high byte
DMA Chan 0 base count low
byte
DMA Chan 0 base count high
byte
DMA Chan 1 base address
low byte
DMA Chan 1 base address
high byte
DMA Chan 1 base count low
byte
DMA Chan 1 base count high
byte
DMA Chan 2 base address
low byte
DMA Chan 2 base address
high byte
DMA Chan 2 base count low
byte
DMA Chan 2 base count high
byte
DMA Chan 3 base address
low byte
DMA Chan 3 base address
high byte
DMA Chan 3 base count low
byte
DMA Chan 3 base count high
byte
40h
7
1
Timer Counter 0 status, bits
[5:0]
Timer Counter 0 base count
low byte
Timer Counter 0 base count
high byte
Timer Counter 1 base count
low byte
Timer Counter 1 base count
high byte
Timer Counter 2 base count
low byte
Timer Counter 2 base count
high byte
Timer Counter 1 status, bits
[5:0]
Timer Counter 2 status, bits
[5:0]
Bit 7 = NMI Enable,
Bits [6:0] = RTC Address
DMA Chan 5 base address
low byte
DMA Chan 5 base address
high byte
DMA Chan 5 base count low
byte
DMA Chan 5 base count high
byte
DMA Chan 6 base address
low byte
DMA Chan 6 base address
high byte
DMA Chan 6 base count low
byte
DMA Chan 6 base count high
byte
DMA Chan 7 base address
low byte
DMA Chan 7 base address
high byte
DMA Chan 7 base count low
byte
DMA Chan 7 base count high
byte
DMA Chan 4-7 Command
2
DMA Chan 4-7 Request
2
2
01h
2
1
3
2
4
02h
2
1
5
2
6
03h
2
1
7
2
41h
1
04h
2
1
42h
1
2
70h
1
05h
2
1
C4h
2
1
2
2
06h
2
1
C6h
2
1
2
2
07h
2
1
C8h
2
1
2
2
08h
6
1
DMA Chan 0-3 Command
2
CAh
2
1
2
DMA Chan 0-3 Request
2
3
DMA Chan 0 Mode:
Bits(1:0) = “00”
DMA Chan 1 Mode:
Bits(1:0) = “01”
DMA Chan 2 Mode:
Bits(1:0) = “10”
DMA Chan 3 Mode:
Bits(1:0) = “11”.
PIC ICW2 of Master controller
PIC ICW3 of Master controller
CCh
2
1
4
2
5
CEh
2
1
6
2
20h
12
1
2
D0h
6
1
2