8253 Microprocessor Quiz and Flashcards: 8253/54 Study Guide

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Questions and Answers

What is the advantage of 8254 over 8253?

More programming modes

Fewer input/output pins

Higher clock frequency range (correct)

More counters

How many counters are present in the 8253/8254 Programmable Interval Timer?

3 (correct)

What is the purpose of the READ BACK COMMAND in the 8253/8254?

To check the count value, programmed mode, and current status (correct)

To set the count value

To interrupt the processor

To program the counter

How many programming modes are available in the 8253/8254?

6 Signup and view all the answers

What is the requirement for programming any of the three counters in the 8253/8254?

The control byte must be written into the control register Signup and view all the answers

What is the significance of the 8253/8254 being compatible with all Intel and most other microprocessors?

It can be used with a wide range of microprocessors Signup and view all the answers

What is the main difference between Mode 2 and Mode 3 of the 8253 operation?

The output remains low for half of the timer period in Mode 3 Signup and view all the answers

Which mode of operation has an output that remains high until the timer has counted to zero?

Mode 4: Software Triggered Strobe Signup and view all the answers

What is the function of the gate input in Mode 1 of the 8253 operation?

It pulses the output low after the rising edge Signup and view all the answers

In Mode 0 of the 8253 operation, what happens when the count reaches zero?

The output goes high and remains high until the next count is reloaded Signup and view all the answers

What is common between Mode 0 and Mode 1 of the 8253 operation?

Both have non-periodic outputs Signup and view all the answers

What determines how the 8253 counter operates?

The control word Signup and view all the answers

What is the maximum operating frequency range of the 8253?

Up to 2.6 MHz Signup and view all the answers

What is the purpose of the CLK pin on the 8253/54?

To provide the input clock frequency Signup and view all the answers

What is the function of the RD pin on the 8253/54?

To send data or status information to the CPU Signup and view all the answers

What type of waveforms can be generated by the OUT pin of the 8253/54?

Square-wave, one-shot, and other square-shape waves Signup and view all the answers

What is the function of the A0 and A1 pins on the 8253/54?

To select the counters and control word register Signup and view all the answers

What is the purpose of the Gate pin on the 8253/54?

To enable or disable the counter Signup and view all the answers

Study Notes

Programmable Interval Timer (PIT) 8253/8254

PIT is used to generate lower frequencies for various applications, such as producing a beep sound.
Compatible with all Intel and most other microprocessors.
Designed as a microcomputer peripheral to solve common timing control problems.

Main Uses of 8253/8254

Measure time delays between external events.
Count the number of times an event occurs.
Cause the processor to be interrupted after a programmed number of external events.
Real-time clock.

Features of 8253/8254

3 independent 16-bit down counters, each working independently and programmable separately.
Counters can be programmed in 6 different modes, all software programmable.
Counting facility in both BCD and Binary number systems.
READ BACK COMMAND allows checking the count value, programmed mode, and current status of the counter.

Modes of Operation of 8253

6 modes of operation, with differences in "OUT" signal shape, periodic or non-periodic, and triggering/start of the counter.
Mode 0: Interrupt on Terminal Count, output goes high when count reaches zero.
Mode 1: Programmable One-Shot, output goes low following the rising edge of the gate input.
Mode 2: Rate Generator, counter continually counts down and output pulses low when count reaches zero.
Mode 3: Square Wave Generator, output remains low for half of the timer period and high for the other half.
Mode 4: Software Triggered Strobe, output remains high until timer counts to zero and then pulses low.

Operating Frequency Range

8253: up to 2.6 MHz.
8254: up to 10 MHz.

Pin Configuration and Function

Data bus (D0-D7): 8-bit bi-directional buses for transferring data.
VCC and GND: +5V power supply and 0V.
CS (Chip Select): enables communication between 8253/54 and CPU.
RD (Read): enables 8253/54 to send data or status information to CPU.
WR (Write): enables CPU to write data or control words into 8253/54.
A0 and A1: select counters and control word register.
CLK: input clock frequency, ranging from 0 to 2 MHz for 8253.
OUT: can have square-wave, one-shot, and other square-shape waves for various duty cycles.
Gate: enables or disables the counter (HIGH = 5V, LOW = 0V).

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Description

This quiz covers the characteristics and pin configuration of the 8253/54 microprocessor, including its operating frequency range, output frequency shape, and pin functions. Test your knowledge of this microprocessor's features and functionality.