BLUE CHIP AOP-12D, User Manual, Page: 45 / 49

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.