DMA controllers in computer system:

•   DMA Controller
•   Part of the I/O device interface
•   DMA Channels
•   Performs functions that in general would be performed by the processor
•   Bus signals that control transfer
•   Provides memory address
•   Keeps track of number of transfers
•   Under control of the processor

INTERFACE CIRCUITS

o   Provides a storage buffer for at least one word of data.

o   Circuitry required connecting an I/O device to a computer bus

o   Contains address-decoding circuitry

o   Contains status flag that can be accessed by the processor.

o   Generates the appropriate timing signals required by the bus control scheme.

o   Performs format conversions

o   Ports

o  Parallel port

o  Serial port

Keyboard to processor connection