Dma hardware (8237 dmac)-microprocessor, Assembly Language

DMA Hardware (8237 DMAC) :

1263_8237.jpg

 

1)Processor contain HOLD/HOLD Acknowledge lines to interact with 8237

o   DMAC can achieve control of ISA bus by asserting HOLD

o   Processor acknowledges with HLDA

 

2)DRQ4 services slave controller Priorities are set as fixed

o   DRQ0 highest and DRQ7 lowest

o   It set at POST

o   It can be reprogrammed for rotating priority

 

3)ISA address/data/control  lines are also linked (not shown)

o   It can access control registers through ports

o   Each channel has a page register associated with   

 

Posted Date: 10/10/2012 9:30:55 AM | Location : United States







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