Programming Example for Standard Function Blocks
9.6 Activation, Startup Program and Cyclic Program
Point-to-point connection CP 440 Installation and Parameter Assignment
136 Manual, 09/2007, A5E00057742-03
Description of the FC 24 (CHK BCC)
The program of the FC24 is largely identical to that of the FC23. At the end, the calculated
block check is compared with the block check of the received data. The #RETVAL output
parameter is output:
● 0: Block check OK or
● -1: Block check error
9.6.4 "CP440 MASTER" Program Example
This example describes the communication between a master and several slaves. You can
find the program sections for the individual slaves in the "CP440 SLAVE" program example.
In OB1 the pattern is set for communication with a partner. The branch table in the "Select
Slave" program section is used for this. Depending on the value in MW 8, either
communication to slave 1 (FC 1 call) or 2 (FC 2 call) is selected. The program can be
adapted to include additional slaves.
In FC 1 a send job ("execute new Send-Job" program section with FC 11 call) and the
associated receive job ("execute Recv-Job" program section with FC 21 call) are called by
the slave for the response. The counter "START_TIMER" for monitoring the response is
started with the send job. If the slave does not respond within the set monitoring time, the
timed period expires and there is a switch to the next slave.
9.6.5 "CP440 SLAVE" Program Example
In FB 40, RECV is called to query whether a job has been received from the master. For this
purpose, in the receive message frame the slave address is compared with its own address.
As soon as there is a job, the reply is sent to the master with the SEND call.
The parameters can be adapted for other slaves in OB 1.
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