Simatic S7 SCL reference: Counters

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Counters - similar to IEC times - can be called in two ways, embedded or with a separate DB. I don't feel like describing this separately, please take a look at the times: IEC Timers.

The function that only counts upwards.

The CTU counts the positive edges of the „CU:“ parameter. As soon as it reaches the value of „PV“ with the calculation, the output „Q“ changes to „TRUE“. The function continues to count. The function can be restarted with the „R“ input.

CTU types:

CTU_SINT / CTU_USINT: the calculation goes with the variable types SINT, USINT
CTU_INT / CTU_UINT: the calculation goes with the variable types INT, UINT
CTU_DINT / CTU_UDINT: the calculation goes with the variable types DINT, UDINT
CTU_LINT / CTU_ULINT: the calculation goes with the variable types LINT, ULINT (only on S7-1500 PLC)

_FB_ CTU (
	CU: BOOL ,	input	Counter signal: The function monitors the positive edge of this binary signal. The counter counted, if signal change from „FALSE“ to „TRUE“.
	R: BOOL ,	input	Reset: Reset CV value.
	PV: INT ,	input	Set value to Q: Value at which the Q output is set
	Q: BOOL ,	output	Result: When the counter reaches „PV“.
	CV: INT / CHAR / WCHAR / DATE	output	Current counter value
);

The example program below can be downloaded here: ctu_example.scl.

Here is a description of how to import the downloaded program to the TIA Portal: Import source code to the TIA portal.

The function that only counts downwards.

The CTD counts the positive edges of the „CD“ parameter, the current counter value of the CV parameter is decremented by one. The function can be restarted with „LD“ input, in this case, the countdown starts again from the „PV“ value. If the current counter value is less than or equal to zero, the „Q“ parameter is set to signal state „TRUE“.

CTD types:

CTD_SINT / CTD_USINT: the calculation goes with the variable types SINT, USINT
CTD_INT / CTD_UINT: the calculation goes with the variable types INT, UINT
CTD_DINT / CTD_UDINT: the calculation goes with the variable types DINT, UDINT
CTD_LINT / CTD_ULINT: the calculation goes with the variable types LINT, ULINT (only on S7-1500 PLC)

_FB_ CTD (
	CD: BOOL ,	input	Counter signal: The function monitors the positive edge of this binary signal. The counter downcounted, if signal change from „FALSE“ to „TRUE“.
	LD: BOOL ,	input	Reset: Load PV value to CV. (Counter newstart)
	PV: INT ,	input	Downcounter start value: The value from which the counter counts down. It can be reloaded with the LD parameter.
	Q: BOOL ,	output	Result: If the current counter value is less than or equal to zero, the parameter is set to signal state „TRUE“.
	CV: INT / CHAR / WCHAR / DATE	output	Current counter value
);

The example program below can be downloaded here: ctd_example.scl.

Here is a description of how to import the downloaded program to the TIA Portal: Import source code to the TIA portal.

The function that counts up- and downwards.

The CTUD counts up the positive edges of the „CU“ input, and counts down with „CD“ input. As soon as it reaches the value of „PV“ with the calculation, the output „QU“ changes to „TRUE“. The function continues to count. The function can be restarted with the „R“ input. The downcounts function can be restarted with „LD“ input, in this case, the countdown starts again from the „PV“ value. If the current counter value is less than or equal to zero, the „QD“ parameter is set to signal state „TRUE“.

CTUD types:

CTUD_SINT / CTUD_USINT: the calculation goes with the variable types SINT, USINT
CTUD_INT / CTUD_UINT: the calculation goes with the variable types INT, UINT
CTUD_DINT / CTUD_UDINT: the calculation goes with the variable types DINT, UDINT
CTUD_LINT / CTUD_ULINT: the calculation goes with the variable types LINT, ULINT (only on S7-1500 PLC)

_FB_ CTUD (
	CU: BOOL ,	input	Counter up signal: The function monitors the positive edge of this binary signal. The counter counted up, if signal change from „FALSE“ to „TRUE“.
	CD: BOOL ,	input	Counter down signal: The function monitors the positive edge of this binary signal. The counter downcounted, if signal change from „FALSE“ to „TRUE“.
	R: BOOL ,	input	Reset upcounter: Reset upcounter CV value.
	LD: BOOL ,	input	Reset downcounter: Load PV value to CV. (Downcounter newstart)
	PV: INT ,	input	Set value to Q / startpoint for downcounter Value at which the Q output is set / The value from which the counter counts down. It can be reloaded with the LD parameter.
	QU: BOOL ,	output	Result: When the counter reaches „PV“.
	QD: BOOL ,	output	Result: If the current counter value is less than or equal to zero, the parameter is set to signal state „TRUE“.
	CV: INT / CHAR / WCHAR / DATE	output	Current counter value
);

Simatic S7 SCL reference: Counters

IEC Counters

CTU: Count up

Example

CTD: Count down

Example

CTUD: Count up

OB121