80C186EC/80C188EC Microprocessor User's Manual

DIRECT MEMORY ACCESS UNIT
Register Name:
Register Mnemonic:
Register Function:
DMA Control Register
DxCON
Controls DMA channel parameters.
15 0
D
M
E
M
D
D
E
C
D
I
N
C
S
M
E
M
S
D
E
C
S
I
N
C
T
C
I
N
T
S
Y
N
1
S
Y
N
0
P
I
D
R
Q
C
H
G
S
T
R
T
W
O
R
D
A1180-0A
Bit
Mnemonic
Bit Name
Reset
State
Function
DMEM
Destination
Address
Space
Select
X
Selects memory or I/O space for the destination
pointer. Set DMEM to select memory space; clear
DMEM to select I/O space.
DDEC
Destination
Decrement
X
Set DDEC to automatically decrement the destination
pointer after each transfer. (See Note.)
DINC
Destination
Increment
X
Set DINC to automatically increment the destination
pointer after each transfer. (See Note.)
SMEM
Source
Address
Space
Select
X
Selects memory or I/O space for the source pointer.
Set SMEM to select memory space; clear SMEM to
select I/O space.
SDEC
Source
Decrement
X
Set SDEC to automatically decrement the source
pointer after each transfer. (See Note.)
SINC
Source
Increment
X
Set SINC to automatically increment the source
pointer after each transfer. (See Note.)
NOTE:
Reserved register bits are shown with gray shading. Reserved bits must be written to a
logic zero to ensure compatibility with future Intel products. A pointer remains constant if
its increment and decrement bits are equal.
Figure 10-13. DMA Control Register
10-20