Chapter 8 20 Points RS485 type Models Instruction 209
MU instruction (Modbus RTU master)
MU function performs Modbus RTU communication at RS485 port. There are 15 MU coils can be used in
ladder mode, MU01~MU0F, and up to 250 MU function blocks diagram in FBD mode.
There can be several MU commands executed at the same time, but only one command can be performed, the
rest are postponed until the performed one is accomplished.
Hardware Configuration:
1. Connect the RS485 port A on each iSmart unit together, also do it to port B, as shown in below figure.
2. Set iSmart in the SET menu to No Remote IO.
3. Set iSmart ID = 01~99.
Function mode corresponding communication function code:
Communication function code
06 (Write Single Register)
10 (Write Multiple Registers)
The M coil used for Modbus function:
Received (M3D)
M3D turns ON after received, then check-up for error. Transferring
target address if there is no error.
Error flag (M3E) communication error flag
Time out flag (M3F) M3F turns ON when the master does not get any response from slave within
certain time. M3F will automatically reset if M3D reset.
The time of time out is depending on communication baud rate as shown in the table below:
、
、
、
To Next Page
Loading...