Modbus Data Base
Publication PUB091-003-00_0119
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Code 05 and 15 - Force Single Coil or Multiple Coils
The output coils are the discrete outputs from the actuator or its digital
control commands. Code 05 writes one coil per message whilst code
15 can write values to several at once.
Code 06 and 16 - Preset Single Register or Multiple Registers
Registers are used for position control and also for digital control and
can be accessed singly, or in multiples with these codes. Function
code 06 writes a single 16 bit register whilst function code 16 can
write several in one transaction.
Code 07 – Read Exception Status
This is a specific short message function code which returns
predetermined discrete data from the MFU. The message is used to
allow fast transfer of a small data packet.
Code 08 - Loopback Diagnostic Test
The purpose of the Loopback Test is to test the communication
system between the Modbus Module and the host. The MFU supports
this test when used with diagnostic code 00, Return Query Data, and
02, Return Diagnostic Register. No other diagnostic test codes are
supported.
Function Code 17 – Report Slave ID
This function code generates a response that contains specific
information about the MFU and actuator (providing the data has been
entered on setup).
Exception Response Codes
Error code 01 will be presented back to the host if the function code in
the data message is not one of those supported by the Modbus
Module or the message length is not as expected.
Error code 02 will be presented back to the host if the Data Address is
not valid for the Modbus Module.
Error code 03 will be presented back to the host if the value to be
written in a coil or register write is not valid for the register or coil
location chosen in the MFU.
Error code 6 will be presented back to the host if the MFU is unable to
respond with a correct message because it is busy.
