3. Suitable soft component
Release serial port instructions, M0's rising edge execute once.
Communication port. Scope: K0 ~ K5. Port0, Port1, Port2 or Port2-RS232 or Port2-
RS485, Port3, Port4, Port5.
When releasing the serial port, the "received" flag SM163 (communication port 2) is
set OFF.
For free communication, if there is no timeout or the timeout time is set too long, the
occupied serial port resources can be released immediately through RCVST
instructions for other communication operations.
Start
M0
Receive
data
SM163
Data
6-3-5．Free communication example
Example 1: In chapter 6-3-3, we give an example of communication between Xinje PLC and
temperature control instrument when explaining why to use free communication. Here is an
example.
Operation steps:
1. Connect the hardware first. Here we use the serial port 2 of the PLC to communicate, that
is, 485 + on the instrument is connected to A of the output port of the PLC, and 485- on the
instrument is connected to B of the output port of the PLC.
2. Set the serial port parameters of PLC according to the communication parameters of
temperature control instrument. The parameters are set as follows. After setting the
parameters, the power can be restarted.
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