a8237 Programmable DMA Controller Data Sheet
Single Request Bit Command
The single request bit command alters a single bit of the 4-bit request
register. See Table 8.
Table 8. Single Request Bit Command Format
Bit
Description
1..0
00 = Channel 0 select
01 = Channel 1 select
10 = Channel 2 select
11 = Channel 3 select
2
0 = Reset request bit
1 = Set request bit
7..3
XXXXX during write, Note (1)
Note:
(1) The X indicates “don’t care.”
Single Mask Bit Command
The single mask bit command alters a single bit of the 4-bit mask register.
See Table 9.
Table 9. Single Mask Bit Command Format
Bit
Description
1..0
00 = Channel 0 mask bit select
01 = Channel 1 mask bit select
10 = Channel 2 mask bit select
11 = Channel 3 mask bit select
2
0 = Reset mask bit
1 = Set mask bit
7..3
XXXXX during write, Note (1)
Note:
(1) The X indicates “don’t care.”
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