How counting modules behave in the different operating modes

General

Counting modules operate in specific ways according to the different PLC operating modes. Knowing about these specific ways is important for programming and debugging the project.

Summary table

The table below shows the special features of counting modules in different operating modes.

	Cold start	Warm restart	STOP	Reconfiguring in online mode
Invalid measurement bit	1	1	0	1
Adjustment parameters: set points, thresholds, preset, measurement period (speed), output period (frequency) %MDr.m.c.r	initial values	unchanged	unchanged	initial values
Commands (direct software actions, various actions, event unmasking) %Qr.m.c.r, %QWr.m.c.r	0	unchanged	unchanged, new commands not sent	unchanged
Information and module data -> processor %IDr.m.c.r, %IWr.m.c.r, %Ir.m.c.r	unchanged if no power outage	unchanged if no power outage	sent	unchanged
Forced objects	unforced	unchanged	unchanged	unchanged
Switches (as a result of Invalid measurement)	0	0	unchanged	0
Outputs	0	0	fallback mode	0

The paragraphs below show the essential properties of these operating modes, seen from a module.

Cold start

A cold start occurs when the application first starts running, when some power is restored, when initialization takes place from Control Expert, or when the Reset button on the processor is pressed.

Parameters are initialized at their set initial values using the configuration editor. The current counter measurement cannot be used (Invalid measurement bit set to 1).

If the module has not had a power outage, the current value of the counter is unchanged although the Invalid measurement bit is set.

The user must set the procedure to be carried out from a cold start.

Warm restart

The program starts again from the program element where the power outage took place, but the outputs remain at 0 until refreshed by the task.

The values of counting application-specific function objects are not changed by a warm restart, except for those involved with the Invalid measurement bit.

If the module has not had a power outage, the current value of the counter is unchanged although the Invalid measurement bit is set.

The user must define the processing procedure to be carried out on a warm restart.

Power outage and restart

When there is a power outage, the application context and time of the outage are stored.

When the power is restored the saved context is compared with that in progress:

if the application context has changed (i.e. loss of system context or new project), the PLC initializes the application: see cold start,
if the application context is the same, the PLC carries out a warm restart.

STOP mode

In STOP mode the user program is not run. However the application-specific counting function does operate: the counter advances according to the status of the physical inputs (IA, IB, IPres or IReset, IEna, ICapt).

Reconfiguring in online mode

This mainly involves debugging a project.

Changes must be confirmed.