80C186EC/80C188EC Microprocessor User's Manual

DIRECT MEMORY ACCESS UNIT
Register Name:
Register Mnemonic:
Register Function:
DMA Destination Address Pointer (Low)
DxDSTL
Contains the lower 16 bits of the DMA Destination
pointer.
15 0
D
D
A
1
5
D
D
A
1
4
D
D
A
1
3
D
D
A
1
2
D
D
A
1
1
D
D
A
1
0
D
D
A
9
D
D
A
8
D
D
A
7
D
D
A
6
D
D
A
5
D
D
A
4
D
D
A
3
D
D
A
2
D
D
A
1
D
D
A
0
A1179-0A
Bit
Mnemonic
Bit Name
Reset
State
Function
DDA15:0
DMA
Destination
Address
XXXXH
DDA15:0 are driven on the lower 16 bits of the
address bus during the deposit phase of a DMA
transfer.
Figure 10-12. DMA Destination Pointer (Low-Order Bits)
10.2.1.2 Selecting Byte or Word Size Transfers
The WORD bit in the DMA Control Register (Figure 10-13) controls the data size for a channel.
When WORD is set, the channel transfers data in 16-bit words. Byte transfers are selected by
clearing the WORD bit. The data size for a channel also affects pointer indexing. Word transfers
modify (increment or decrement) the pointer registers by two for each transfer, while byte transfers
modify the pointer registers by one.
10-19