Siemens SIMATIC S7 CP340 Programming Manual page 50

5 MODBUS RTU Protocol communication
REQ
DB_NO
DBB_NO
LEN
R_TYP
R
DONE
ERROR
STATUS
Other
parameters
Table 13: Parameter definition of FB8 P_SND_RK
Fig. 90: Invoke FB8 P_SND_RK from OB1
4. Invoke Receive Function Block FB7 P_RCV_RK from Libraries -> CP PtP ->
CP341 and distribute instance data block DB7 to it. Set LADDR as the input
start logic address 256 in hardware configuration.
CP340/CP341/CP440/CP441 Communication and Programming
Entry-ID: 88867653, V1.0,
example
trigger bit of Send Data, rising edge trigger, which is M0.0 in this
example
Send Data block number, which is 1(DB1) in this example
Start address of Send Data, which is 0(DB1.DBB0) in this example
Length of send data, which is 6 in this example
"X" refers to extended data block, which must be in capital form here.
Cancel communication, which is not available in this example
send complete bit, which is TRUE if Send completes and has no error
error bit, TRUE indicating that it has an error
Status word, ID error code. See Modbus Master Manual - Chapter 7 for
related description.
Not applicable in this example.
02/2014
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