MODBUS FUNCTION CODES & SUPPORTED CODES
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Data and Control Functions
CODE NAME
01
Read Coil Status
X
Digital output from the slave
02
Read Input Status
X
Status of digital inputs to the slave
03
Read Holding Registers
X
General purpose register within the slave
04
Read Input Registers
X
Collected data from the field by the slave
05
Force Single Coil
X
Digital output from the slave
06
Preset Single Registers
X
General purpose register within the slave
07
Read Exception Status
08
Diagnostics
X
09
Program 484
10
Poll 484
11
Fetch Comm. Event Counter
Fetch a status word and an event counter
12
Fetch Comm. Event Log
A status word, an event counter, a message count and a field of event bytes
13
Program Controller
14
Poll Controller
15
Force Multiple Coils
X
Digital output from the slave
16
Preset Multiple Registers
X
General purpose register within the slave
17
Report Slave ID
Slave type / ‘RUN’ status
18
Program 884/M84
19
Reset Comm. Link
20
Read General Reference
21
Write General Reference
22
Mask Write 4X Register
23
Read/Write 4X Register
24
Read FIFO Queue
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Exception Codes
CODE NAME
01
Illegal Function
X
Function code is not allowable for the slave
02
Illegal Data Address
X
Address is not available within the slave
03
Illegal Data Value
X
Data is not valid for the function
04
Slave Device Failure
05
Acknowledge
06
Slave Device Busy
07
Negative Acknowledge
08
Memory Parity Error
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Diagnostic Subfunctions
CODE NAME
00
Return Query Data
X
Loop back test
01
Restart Comm. Option
X
Reset the slave and clear all counters
02
Return Diagnostic Register
X
Contents of the diagnostic data (2 bytes)
03
Change ASCII Input Delimiter
X
Delimiter character of ASCII message
04
Force Listen Only Mode
X
Force the slave into Listen Only Mode
R5-NM1
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EM-6104 Rev.8 P. 4 / 7