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Appendix C
Page
39
Blue Chip Technology Ltd.
01270146.doc
Page 39
Mask Register
Port 0AH
7
NOT
USED
6
NOT
USED
5
NOT
USED
4
NOT
USED
3
NOT
USED
2
CLR/SET
MASK
1
MASK
Bit 1
0
MASK
Bit 0
CLR/SET Mask
0
Clear Mask Bit
1
Set Mask Bit
Mask
Bit 1
Bit 0
FUNCTION
0
0
Channel 0 select
0
1
Channel 1 select
1
0
Channel 2 select
1
1
Channel 3 select
Setting a mask bit for a particular channel disables the DMA operation on that
channel.
Status Register
Port 0BH READ
7
CHAN
3
DMA
RQ
6
CHAN
2
DMA
RQ
5
CHAN
1
DMA
RQ
4
CHAN
0
DMA
RQ
3
CHAN
3
at
TC
2
CHAN
2
at
TC
1
CHAN
1
at
TC
0
CHAN
0
at
TC
DMA RQ
1 = DMA Request made on channel N
AT TC
1 = Channel N has reached Terminal Count (TC)
The status register indicates which channels have made a DMA request and
which channels have reached Terminal Count. Terminal count is set when the
number of bytes specified by the TRANSFER LENGTH register have been
transferred.
Содержание AOP-12D
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