Siemens SIMATIC CP 541 Manual page 125

STL
FB 11
Segment 1
Name :R 3<=0
:Q F 6.7
:BEC
:
:Q DB 10
:
:L DW 1
:T FW 10
:L DW 2
:T FW 12
:
:
:L DW 5
:T FW 18
:
:
:
:
:
:AN F 6.7
:S F 6.7
:BE
FB 12
Segment 1
Name :S 3=>0
:Q F 8.7
:BEC
:
:Q DB 10
:L KY 4,0
:T DW 33
:
:
:
:
:
:L FW 20
:T DW 34
:L FW 22
:T DW 35
:
:AN F 8.7
:S F 8.7
:
:BE
Communications Processor CP 541
EWA 4NEB 812 6188-02
Explanation
Receive block
Test whether L1 message is present
If not, block end
Open receive mailbox
Intermediate storage of receive data
for further processing
=======================================
Program section to evaluate
receive data
=======================================
Indicates to operating system that
ready to receive again
Send block
If send mailbox blocked by operating
system, then block end
Open send mailbox
Send 4 bytes to station 0 DP master
=======================================
Program section to reserve
send data
=======================================
Write send data into transfer area
Release send mailbox for operating
system
Program Examples
H-11