Using A Trigger When Monitoring Or Modifying Plc Tags - Siemens S7-1200 System Manual

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The following options are available for modifying tags:

● "Modify to 0" sets the value of a selected address to "0".

● "Modify to 1" sets the value of a selected address to "1".

● "Modify now" immediately changes the value for the selected addresses for one scan

● "Modify with trigger" changes the values for the selected addresses.

● "Enable peripheral outputs" disables the command output disable and is available only

To monitor the tags, you must have an online connection to the CPU.

You use the buttons at the top of the watch table to select the various functions.

Enter the tag name to monitor and select a display format from the dropdown selection. With

an online connection to the CPU, click the "Monitor" button to display the actual value of the

data point in the "Monitor value" field.

Using a trigger when monitoring or modifying PLC tags

Triggering determines at what point in the scan cycle the selected address will be monitored

or modified.

At scan cycle start

At scan cycle end

At transition to

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG

This function does not provide feedback to indicate that the selected addresses were

actually modified. If feedback of the change is required, use the "Modify now" function.

when the CPU is in STOP mode.

Types of triggers

Continuously collects the data

Permanent: Continuously collects the data at the start of the scan cycle, after

the CPU reads the inputs

Once: Collects the data at the start of the scan cycle, after the CPU reads the

Permanent: Continuously collects the data at the end of the scan cycle, before

the CPU writes the outputs

Once: Collects the data once at the end of the scan cycle, before the CPU

writes the outputs

Permanent: Continuously collects data when the CPU transitions to STOP

Once: Collects the data once after the CPU transitions to STOP

14.11 Monitoring and modifying values in the CPU

Online and diagnostic tools