Programming instructions

LESSON 12 – Timers and Counters

Timers and counters are a standard part of a PLC program. This section will cover the

various types of timers and counters available in the FX-Series PLCs as well as how to

code them. Exercises will allow the user to demonstrate their understanding of the

concepts.

Lesson Objectives: At the conclusion of this lesson, you will be able to…

9 Describe the different types of timers

9 Know the availability of timers and counter

9 Describe the format for timer and counter instructions

9 Describe timer and counter limitations

9 List the types of presets available to timers and counters

9 Write a program using timers

Materials: FX-Series PLC Training Manual

FX-series Demo Kit

FX3U Programming Manual – Basic and Applied Instructions

12.1 Timers

Availability

FX3U PLCs have 512 timers.

FX1N, FX2N, and FX2NC PLCs have 256 timers.

FX1S PLCs have 64 timers. The time base is dependent upon the address used

in the timer instruction. In the FX1S, a special relay bit (address M8028) can be

set to convert 31 of the 100ms timers to 10ms timers.

Types

• 100ms (.1 second)

• 10ms (.01 second)

• 1ms (.001 second)

PLC Timer Address

Time Base FX1S FX1N/FX2N/FX2NC FX3U

100ms 0-62 0-199 0-199

10ms 32-62 200-245 200-245

1ms (Retentive) - 246-249 246-249

100ms (Retentive) - 250-255 250-255

1ms 63 - 256-511