Description
The "Measure program runtime" instruction is used to measure the runtime of the entire program, individual blocks or command sequences.
If you want to measure the runtime of your entire program, call the instruction "Measure program runtime" in OB1. Measurement of the runtime is started with the first call and the output RET_VAL returns the runtime of the program after the second call. The measured runtime includes all CPU processes that can occur during the program execution, for example, interruptions caused by higher-level events or communication. The instruction "Measure program runtime" reads an internal counter of the CPU and write the value to the IN-OUT parameter MEM. The instruction calculates the current program runtime according to the internal counter frequency and writes it to output RET_VAL.
If you want to measure the runtime of individual blocks or individual command sequences, you need three separate networks. Call the instruction "Measure program runtime" in an individual network within your program. You set the starting point of the runtime measurement with this first call of the instruction. Then you call the required program block or the command sequence in the next network. In another network, call the "Measure program runtime" instruction a second time and assign the same memory to the IN-OUT parameter MEM as you did during the first call of the instruction. The "Measure program runtime" instruction in the third network reads an internal CPU counter and calculates the current runtime of the program block or the command sequence according to the internal counter frequency and writes it to the output RET_VAL.
The "Measure program runtime" instruction uses an internal high-frequency counter to calculate the time. If the counter overruns, the instruction returns values <= 0.0. This can occur up to once per minute for S7-1200 CPUs with firmware version <V4.2. Ignore these runtime values.
|
Note The runtime of a command sequence cannot be determined exactly, because the sequence of instructions within a command sequence is changed during optimized compilation of the program. |
Parameters
The following table lists the parameters of the "Measure program runtime" instruction:
|
Parameters |
Declaration |
Data type |
Memory area |
Description |
|---|---|---|---|---|
|
EN |
Input |
BOOL |
I, Q, M, D, L, T, C or constant |
Enable input |
|
ENO |
Output |
BOOL |
I, Q, M, D, L |
Enable output |
|
MEM |
InOut |
LREAL |
I, Q, M, D, L |
The content is for internal purposes only. |
|
RET_VAL |
Output |
LREAL |
I, Q, M, D, L |
Returns the measured runtime in seconds |
Example
The following example shows how the instruction works based on the runtime calculation of a program block:
Network 1:
Network 2:
Network 3:
When the "TagIn1" operand in network 1 has the signal state "1", the instruction is executed. The starting point for the runtime measurement is set with the first call of the instruction and buffered as reference for the second call of the instruction in the "TagMemory" operand.
The "Best_before_date" program block FB1 is called in network 2.
When the FB1 program block has been executed and the "TagIn1" operand has the signal state "1", the instruction in network 3 is executed. The second call of the instruction calculates the runtime of the program block and writes the result to the output RET_VAL.
You can find a more detailed example of how you can measure the total cycle time of a program in the Siemens Industry Online Support under the following entry ID: 87668055