New Functions in Version V4.02
New Functions: Forcing with S7-300 Modules
The following table provides an overview of the functions and summarizes the differences between forcing and modifying.
Feature / Function | Force | Modify | ||
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| with | with |
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Bit memory (M) |
| yes | no | yes |
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Timers and counters (T, C) | no | no | yes | |
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Data blocks (DB) | no | no | yes | |
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Peripheral inputs (PIB, PIW, PID) | yes | no | no | |
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Peripheral outputs (PQB, PQW, PQD) | yes | yes * | yes | |
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Inputs and outputs (I, Q) | yes | yes * | yes | |
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Defining triggers | always trigger | always trigger | yes | |
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| immediately | immediately | (once or every |
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| cycle) |
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Function only affects variable in visible | affects all | affects all | yes | |
area of active window. | force values | force values |
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User program can overwrite the modify/ | no | yes * | yes | |
force values. |
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Replacing the force value effective without | yes | yes | no | |
interruption. |
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The variables retain their values when | yes | yes | no | |
application is exited. |
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Variables retain their values after the | yes | yes | no | |
connection to the CPU is broken. |
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Variables retain their values after power | yes | yes | no | |
off, provided CPU has battery backup. |
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Address error permitted: | no | no | yes | |
e.g.: | IW1 modify/force value: 1 |
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| the last |
| IW1 modify/force value: 0 |
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| becomes |
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| effective | |
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*The inputs
- read instructions (for example, L PIW x)
- write programming device/operator panel functions
The outputs occupied by force values can be overwritten with:
-write instructions (for example, T PQB x)
-write programming device/operator panel functions
Supplement to the STEP 7 User Manual V4.0 | 17 |