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Preview:
The 8251A is a widely used communication interface chip
that was developed by Intel. It is a programmable Universal
Synchronous Asynchronous Receiver Transmitter (USART)
chip, commonly known as a serial communication controller.
The 8251A is designed to facilitate serial data
communication between a microprocessor-based system and
peripheral devices.
3. z
Here are some basic details about the 8251A
communication interface:
1.Function: The 8251A performs three main functions:
i. Data transmission
ii. Data reception
iii. Synchronous/Asynchronous mode control.
It handles the serialization and deserialization of data
It manages the timing and synchronization of the
transmitted and received data.
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2. Data Format: The 8251A supports both asynchronous and
synchronous serial communication.
In asynchronous mode, it supports various data formats, including
5, 6, 7, or 8 data bits, with selectable parity (even, odd, or no
parity) and one or two stop bits.
In synchronous mode, it supports synchronous data transmission
and reception with an external clock.
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3. Buffering: The 8251A has built-in data buffers to store
the incoming and outgoing data.
It uses a First-In-First-Out (FIFO) buffer for data storage,
which helps in managing the data flow between the
microprocessor and the peripheral devices.
4.Control Registers: The 8251A has several control registers
to configure and control its operation.
These registers include mode control register, command
register, status register, data register, and control word
register.
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5.Interrupts: The 8251A can generate interrupts to the
microprocessor based on different conditions, such as the
availability of data or the completion of a data transfer.
These interrupts allow the microprocessor to efficiently
handle the data transfer process and perform other tasks
while waiting for data.
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6.Interface: The 8251A uses a parallel interface to
communicate with the microprocessor.
It typically connects to the microprocessor's address, data,
and control buses.
It also requires additional external circuitry, such as level
shifters and drivers, to connect to the serial lines of the
communication system.
