Modular Structure Of The Plc Program - Fagor CNC 8060 Installation Manual

I n s t a l l a t i o n m a n u a l .
3.2

Modular structure of the PLC program.

The PLC program may comprise the following modules. Every module must begin with the
directive instruction that defines it (CY1, PRG, PE) and end with the directing instruction END.
• First Cycle module (CY1).
• Main module (PRG).
• Periodic module (PE).
First Cycle module.
It is an optional module. The module begins with the directing instruction CY1 and ends with
the directive instruction END.
The PLC executes the first cycle module onlyonce when starting up the PLC program. This
modules is used to initialized the various resources and variables before executing the main
program.
Main module.
The main module begins with the directing instruction PRG and ends with the directive
instruction END.
The PLC executes the main module cyclically with the frequency set by parameter
PRGFREQ. This module is in charge of analyzing and modifying the CNC inputs, outputs
and variables. The PRG execution takes about 100 µs.
Parameter PRGFREQ indicates how often (every how many CNC cycles) the PLC executes
a full cycle of the main module. Hence, with a sampling period of 4 ms (LOOPTIME=4) and
a frequency of 2 cycles (PRGFREQ=2), the PLC executes the main module every 4 x 2 =
8ms.
Periodic module.
It is an optional module. The periodic module begins with the directing instruction PE and
ends with the directive instruction END.
The PLC executes the periodic module cyclically with the frequency set by the directive
instruction PE, between 1 and 2147483647 ms and never less than the loop time (parameter
LOOPTIME). This module could be used to execute tasks that do not need to be executed
at every PLC cycle.
For example, a task to be performed every 30 seconds could be defined in a periodic module
using the instruction (PE 30000).
3.
CNC 8060
CNC 8065
(R : 1709)
EF
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