DIRECT MEMORY ACCESS UNIT
10-12
Figure 10-8. DMA Source Pointer (Low-Order Bits)
The address space referenced by the source and destination pointers is programmed in the DMA
Control Register for the channel (see Figure 10-11 on page 10-15). The SMEM and DMEM bits
control the address space (memory or I/O) for source pointer and destination pointer, respective-
ly.
Automatic pointer indexing is also controlled by the DMA Control Register. Each pointer has two
bits, increment and decrement, that control the indexing. If the increment and decrement bits for
a pointer are programmed to the same value, then the pointer remains constant. The programmed
data width (byte or word) for the channel automatically controls the amount that a pointer is in-
cremented or decremented.
Register Name:
DMA Source Address Pointer (Low)
Register Mnemonic:
DxSRCL
Register Function:
Contains the lower 16 bits of the DMA Source pointer.
Bit
Mnemonic
Bit Name
Reset
State
Function
DSA15:0
DMA
Source
Address
XXXXH
DSA15:0 are driven on the lower 16 bits of the
address bus during the fetch phase of a DMA
transfer.
15
0
D
S
A
1
D
S
A
2
D
S
A
3
D
S
A
0
D
S
A
5
D
S
A
6
D
S
A
7
D
S
A
4
D
S
A
9
D
S
A
1
0
D
S
A
1
1
D
S
A
8
D
S
A
1
3
D
S
A
1
4
D
S
A
1
5
D
S
A
1
2
A1177-0A
Содержание 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
Страница 229: ......
Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
Страница 255: ......
Страница 283: ......
Страница 284: ...11 Math Coprocessing...
Страница 285: ......
Страница 302: ...12 ONCE Mode...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
Страница 373: ......
Страница 396: ...Index...
Страница 397: ......