Siemens SIMATIC S7-400 CP 440 - CP440 1 CYC Program Example

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Programming Example for Standard Function Blocks

9.6 Activation, Startup Program and Cyclic Program

Point-to-point connection CP 440 Installation and Parameter Assignment

134 Manual, 09/2007, A5E00057742-03

The "Enable Receive Data" program section:

Before data can be received, the receive enable (RECV_EN_R) at block RECV_440 must be

set to "1".

"RECV_NDR=1" program section:

When RECV_NDR is set, new data has been received and the RECV_COUNTER_OK

receive counter is incremented.

"RECV_ERROR=1" program section:

If execution is unsuccessful (i.e. if the error bit is set at the parameter output of RECV_440),

the RECV_COUNTER_ERR error counter is incremented. The RECV_STATUS is copied,

because it is overwritten with 0 in the next run and it will thus not be possible to read it out.

All relevant values can be observed for test purposes in the variable table.

9.6.2 "CP440 1 CYC" Program Example

This example is set up identically to the example "CP440 SEND RECV". However, the FC 21

has been changed to allow a SEND job to be processed cyclically.

Description of FC 21 (SEND)

The procedure for processing a SEND job cyclically is as follows:

● At each block call, SEND_440 is run through with SEND_REQ=0. If neither SEND_DONE

nor SEND_ERROR are present, the block is terminated.

● If SEND_DONE is present, SEND_440 is run through again with SEND_REQ=1.

● If SEND_ERROR is present, SEND_440 is run through with SEND_REQ=0 and then with

SEND_REQ=1.

To ensure that SEND_440 can be run through with SEND_REQ=1 in the very first pass, the

SEND_STARTUP_ENDED bit is also evaluated in the program section "Check if

SEND_DONE or SEND_ERROR or not first Cycle". This bit is at 0 during the first pass and is

then fixed at 1.

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