DIRECT MEMORY ACCESS UNIT
10-10
Figure 10-6. Examples of DMA Priority
10.1.10.1.2
Rotating Priority
Channel priority rotates when the channels are programmed as both high or both low priority. The
highest priority is initially assigned to channel 1 of the module. After a channel performs a trans-
fer, it is assigned the lower priority. When requests are active for both channels, the transfers al-
ternate between the two. Channel 1 is reassigned high priority whenever the bus is released (that
is, at the end of a destination-synchronized transfer or when DMA requests are no longer active).
10.2 PROGRAMMING THE DMA UNIT
A total of six Peripheral Control Block registers configure each DMA channel.
10.2.1 DMA Channel Parameters
The first step in programming the DMA Unit is to set up the parameters for each channel.
10.2.1.1
Programming the Source and Destination Pointers
The following parameters are programmable for the source and destination pointers:
•
pointer address
•
address space (memory or I/O)
•
automatic pointer indexing (increment, decrement or no change) after transfer
Channel
Priority
Synch
Both Requests Asserted
0
Low
SRC
1
Low
SRC
Channel
Priority
Synch
0
High
SRC
1
Low
SRC
Channel
Priority
Synch
0
High
Dest
1
Low
SRC
Channel 1 Channel 0 Channel 1 Channel 0
Channel 0
Channel 1 Channel 1
Channel 1
Channel 0
Channel 1
Channel 0
Channel 0
Channel 0 Completes
All Transfers
Destination Synch Releases Bus
Etc.
Etc.
Etc.
A1190-0A
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...
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Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 396: ...Index...
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