RT: Reset timer (S7-1200, S7-1500) - STEP 7

Description

You can use the "Reset timer" instruction to reset an IEC Timer to "0". You specify the IEC Timer to be reset by entering the name of the data block that contains the structure of the IEC Timer in the placeholder above the instruction.

The instruction is only executed if the result of logic operation (RLO) at the box input is "1". When the instruction is executed the structure components of the IEC Timer are reset to "0" in the specified data block. If the RLO at box input is "0", the instruction is not executed.

The instruction does not influence the RLO. The RLO at the box input is transferred directly to the box output.

You must assign a IEC Timer declared in the program to the "Reset timer" instruction.

Updating of the actual values

The instruction data is updated only when the instruction is called and not each time the assigned IEC Timer is accessed. The query of the data is only identical from the call of the instruction to the next call of the instruction.

Danger

Danger when reinitializing the actual values Reinitializing the actual values of an IEC timer while the timer is running disrupts the function of the IEC timer. Changing the actual values can result in inconsistencies between the program and the actual process. This can cause serious damage to property and personal injury. The following functions can cause the actual values to be reinitialized: Loading the block with reinitialization Loading snapshots as actual values Controlling or forcing the actual values The "WRIT_DBL" instruction Before you execute these functions, take the following precautions: Make sure that the plant is in a safe state before you overwrite the actual values. Make sure that the IEC timer has expired before initializing its actual values. 　 If you overwrite the actual values with a snapshot, make sure that the snapshot was taken at a time when the system was in a safe state. Make sure that the program does not read or write the affected data during transmission.

Parameters

The following table shows the parameters of the instruction "Reset timer":

For additional information on valid data types, refer to "See also".

Example

The following example shows how the instruction works:

The "Generate on-delay" instruction executes when the signal state of the "Tag_Input_1" operand changes from "0" to "1". The IEC Timer stored in the instance data block "TON_DB" is started with the time duration that is specified by the operand "Tag_PT".

If the operands "Tag_Input_2" and "Tag_Input_3" have the signal state "1", the "Reset timer" instruction is executed and the IEC Timer stored in the data block "TON_DB" is reset.