Programmable Peripheral Devices

Programmable peripheral devices were introduced by Intel to increase the overall performance of the system. These devices along with I/O functions, they perform various other functions such as time delays, counters and interrupt handling. These devices are nothing but a combination of many devices on a single chip. A programmable device can be set up to perform specific function by writing a code in the internal register. As this code controls the function of the device it’s called control word and internal register in which it is stored is called Control Register.

INTEL developed some peripheral devices for processors like 8085/8086/8088. The peripheral devices includes

8255 – Parallel Communication Interface (PPI)

8251 – Serial communication Interface (USART- Universal Synchronous/Asynchronous Receiver/Transmitter)

8257 – DMA Controller

8279 – Keyboard/Display Controller

8259 – Programmable Interrupt controller

8254 – Programmable Timer

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