Chapter 5 Relay Ladder Logic Programming 117
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12BMU (Modbus) (Only CD type model)
MU function performs Modbus RTU communication at RS485 port. There are 15
MU coils: MU01~MU0F.
Remote IO and IO Link have higher priority than MU to use RS485 port. MU is
executed when the remote IO setting in the system is disabled (No Remote IO) and ID is
not 0.
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.
Func
tion mode corresponding communication function code:
Communication function code
06 (write single register)
10 (write multiple registers)
Th
e coils used for MU function:
M3D turns ON after received, then check-up for error. Transferring data to
target address if there is no error.
M3F turns ON when the master does not get any response from slave within
certain time. M3F will automatically reset if M3D reset.
Th
e time of time out depends on the baud rate as shown in the below table.
、
、
、
Th
ere are 5 parameters in MU function as shown below.
①
②
ID number of the target unit: range from 0 to127
③
The address of target register in that unit:
1) address is assigned to a constant, range from 0000 to ffff;
• Just do the read/write function to the register with one data
length/address in mode 1 and 3.
• Do the read/write function to the coil with one data length/addre
ss
i
n mode 4 and 5.
2) The address refers to the content of DR coil, and the value of coil
behind this one determines how many registers or coil will be read or
write, see the next five pages for more information.
④
DR code, store sending/receiving data from this DR
⑤
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