programmable timer 8253/8254
Post on 15-Aug-2015
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8254 / 8253
THE PROGRAMMABLE INTERVAL TIMER
8254 / 8253
• Programmable interval timer/counter
• Includes three independent 16-bit counters
• Has six modes of operation
• Operation:-– A 16-bit count is loaded on the counter and on
command it starts decrement– When the count reaches zero it generates a
pulse
8254 Block Diagram
8254 Control Word Format
Mode 0: Interrupt on Terminal Count
Mode 1 : Programmable One-Shot
Mode 2 : Rate Generator Clock
Mode 3: Square Wave Generator
Mode 4: Software Triggered Strobe
Mode 5: Hardware Triggered Strobe
Read-Back Command Format
Status Byte
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