Siemens FM 450-1 - Page 45

Description of the symbols
The tables lists the symbols used in the example. You specify your own symbol assignments in
the S7 symbol table.
Table 6-1 Symbols in the user program
Symbols used Absolute (example) Comment
CHANNEL1 DB 1 Data block for FC°CNT_CTRL
CHANNEL1.LOAD_VAL DB1.DBB14 Counter value speci󹪝ed in DB 1
INITIATE M 10.0 Initiation bit generated to meet technological requirements
LOAD_DIRECT M 20.0 Accept counter value directly
START M 20.1 Start counter
GATE_STOP M 20.2 Close counter gate
ERR_ACKN M 20.3 Acknowledge operator error
LOAD_INDIRECT M 20.4 Load counter value in preparation
COMP1_LOAD M 20.5 Load comparison value 1
COMP2_LOAD M 20.6 Load comparison value 2
RES_SYNCHRON M 20.7 Reset synchronization status bit
RES_ZERO M 21.0 Reset zero crossing, over󹪞ow and under󹪞ow status bit
OPERATOR_ERROR M 21.1 Operator error occurred
CHANNEL 1.OT_ERR_B DB1.DBX40.0 Operator error information in DB 1
Description of the sequence
Prerequisite:
The value to be transferred must have been entered in the DB°1.
The load value is transferred and started:
When the FC is called, the load value of a channel is transferred to the FM 450-1. Calling the FC
°CNT_CTRL selects either the L_DIRECT parameter or the L_PREPAR parameter. The L_DIRECT
selection bit speci󹪝es that the load value will be loaded directly onto the counter (L_DIRECT=1).
The L_PREPAR selection bit speci󹪝es that the load value is to be stored in the load register
(L_PREPAR=1). The load value in the load register is then loaded onto the counter when the
counter is next set. L_PREPAR=1 prepares a new counter value. Load value transfer lasts a
minimum of 3 FC calls.
The FC must be called until it has reset the selected initiation bit (L_DIRECT or L_PREPAR). While
the job is in progress the I/O parameter remains set. The FC°CNT_CTRL does not output an error
message regarding data exchange with the FM.
If the FC CNT_CTRL resets the parameter you had set, the FM 450-1 has accepted the load value.
The read-back load value stored in the DB°1 is updated by the FC°CNT_CTRL.
You must generate the "initiation" bit to comply with your technological requirement. This bit
may be set at "1" for one cycle only. Please note, that the FC must be called until the I/O parameter
of the FC CNT_CTRL is reset.
Program
6.4 Example application
Counter module FM 450-1
Equipment Manual, 03/2022, A5E03648739-AC 45