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Appendix C
Page
37
Blue Chip Technology Ltd.
01270146.doc
Page 37
The DMA Controller Registers
In order to begin a DMA transfer there are several registers within the DMA
controller which need to be configured. The relevant registers are described
below:-
Mode Register
Port 0BH
7
MODE
Bit 1
6
MODE
Bit 0
5
AUTO
INC/
DEC
4
AUTO
INIT.
3
TRANS
MODE
Bit 1
2
TRANS
MODE
Bit 0
1
CHAN
SEL
Bit 1
0
CHAN
SEL
Bit 0
Mode Bits
Bit1
Bit 0
FUNCTION
0
0
Demand Mode
0
1
Single Mode
1
0
Block Mode
1
1
Not Used
The mode bits set the particular mode for the channel, normally this will be set
for SINGLE mode.
Auto INC/DEC
0
Increment Address
1
Decrement Address
When a DMA transfer takes place, the transfer address can either be
incremented or decremented after each transfer selected by this bit.
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