User`s guide

•

Operation Theorem

• RL1 & RL0 - Select Read/Load operation ( Bit 5 & Bit 4)

RL1 RL0 OPERATION

0 0 COUNTER LATCH FOR STABLE READ

0 1 READ/LOAD LSB ONLY

1 0 READ/LOAD MSB ONLY

1 1 READ/LOAD LSB FIRST, THEN MSB

• M2, M1 & M0 - Select Operating Mode ( Bit 3, Bit 2, & Bit 1)

M2 M1 M0 MODE

0 0 0 0

0 0 1 1

x 1 0 2

x 1 1 3

1 0 0 4

1 0 1 5

• BCD - Select Binary/BCD Counting ( Bit 0)

0 16-BITS BINARY COUNTER

1 BINARY CODED DECIMAL (BCD) COUNTER (4

DIGITAL)

Note The count of the binary counter is from 0 up to

65,535 and the count of the BCD counter is from 0

up to 9,999

Mode Definitions

In 8254, six operating modes can be selected. they are:

•

Mode 0:

Interrupt on Terminal Count

•

Mode 1:

Programmable One-Shot.

•

Mode 2:

Rate Generator.

•

Mode 3:

Square Wave Rate Generator.

•

Mode 4:

Software Triggered Strobe.

•

Mode 5:

Hardware Triggered Strobe.

All detailed description of these six modes are written in Intel Microsystems

Components Handbook Volume II Peripherals.