Sequential Call Of Fc "Readwrite - Siemens SIMATIC S7-1200 Manual

3 Mode of Operation

Sequential call of FC "ReadWrite"

3.5.2
To execute several register accesses successively, the parameters have to be
handed to the FC "ReadWrite" in the form of a sequencer.
In the OB "Main" this is presented in networks 4 through 7.
Task
The following actions are to be performed successively:
1. Reading input register 16#D015 of fan 1
2. Reading holding registers 16#D108 through 16#D10D of fan 2 (see chapter
3.5.1)
3. Writing the value 1 to holding register 16#D105 of fan 1 ("internal parameter
set") (corresponds to: parameter set 2)
Figure 3-8
The sequencer is started in network 4. The step is displayed in white font. The jobs
are processed in the networks 5 through 7. A job consists of the parameter
handover and the subsequent action in case of the ready message ("done").
Subsequently, the program continues with the next step.
The steps are called in the reverse order of the networks.
This is necessary to prevent "sliding through" the steps.
You can check the function of the sequencer using the watch table "ReadWrite":
Figure 3-7
Successful writing to holding register 16#D105 is accomplished by reading the
register again or using
Controlling several fans (ebm-papst) via Modbus RTU
Entry ID: 109476801, V2.0,
shows the program sequence.
Cyclically retrieved values (input
or Figure 3-7
09/2018
registers):
in line 38.
24