User Documentation

Communications
80 1435710000/01/05.13
Slave address
Slave address is an individual instrument number on the slave side and is set within the range of 1 to 247
(01H to F7H) for Modbus communication. The Master identifies Slaves by the slave address of the requested
message.
The Slave informs the Master which Slave is responding to the Master by placing its own address in the
response message. The Slave address 0 (00H, broadcast address) can identify all Slaves connected.
However, Slaves do not respond.
Function code:
Function code is command code for the Slave to undertake the following types of action.
Function code Contents
03(03H) DT Read
06(06H) DT1 Word write
16(10H) DT Multiple data write
Function code is used to discern whether the response is normal (acknowledgement) or if any error
(negative acknowledgement) has occurred when a Slave returns a response message to the Master.
When an acknowledgement is returned, the Slave simply returns the original function code. When negative
acknowledgement is returned, the MSB of the original function code is set as 1 for the response.
For example, when the Master sends a request message setting 00H to function code by mistake, the Slave
returns 80H by setting MSB to 1, because the former is an illegal function.
For negative acknowledgement, the exception codes below are set to data of the response message and
returned to the Master in order to inform it of what kind of error has occurred.
Exception code Contents
1(01H) Illegal Function (non-existent function)
3(03H) Illegal data value (value out of the device numbers)
Notes
1) Even if it commands to write (06H.10H) to a non-existent data address, the Slave responds with an
acknowledgement. However, it does not write.
2) Even if it commands to write the value out of the setting range, the Slave responds with an acknowl-
edgement. However, it does not write.
3) The maximum number of reading Slaves is 26 (57-byte), the maximum number of writing Slaves is 23
(55-byte).