DMA (Direct Memory Access): is a procedure for transferring data directly between controller and memory without the help of CPU.
DMA device: is like a separate CPU with functions related to data transfer, such as:
– shuts the CPU down for short periods
– seizes control of the system bus
– transfers data between memory and external device without the intermediation of CPU
Disk controller: accepts commands from CPU such as:
– select disk drive
– set up DMA registers
– return current sector address
– return current track address
– move head in/out one track
– move head to track 0
– read/write current sector
Status port: contains the result of a query from CPU or status
Control port: commands for the controller are placed
DMA address registers: they receive addresses from CPU
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