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Ceiec Electric Technology
Chapter 5 Modbus Register Map
This chapter provides a complete description of the Modbus register map (
Protocol Versions 1.0
and
above) for the PMC-630E Multifunction Ethernet to facilitate the development of 3
rd
party
communications driver for accessing information on the PMC-630E.
The PMC-630E supports the following Modbus functions:
1)
Read Holding Registers (Function Code 0x03)
2)
Force Single Coil (Function Code 0x05)
3)
Preset Multiple Registers (Function Code 0x10)
4)
Read General Reference (Function Code 0x14)
For a complete Modbus Protocol Specification, please visit http://www.modbus.org.
Read General Reference Packet Structure (Function Code 0x14)
Read Reference Request Packet
(Master Station to PMC-630E)
Read Reference Response Packet
(PMC-630E to Master Station)
Slave Address
1 Byte
Salve Address
1 Byte
Function Code (0x14)
1 Byte
Function Code (0x14)
1 Byte
Byte Count
1 Byte
Byte Count
1 Byte (NxN
0
+2)
Sub-Req X, Reference Type (0x06)
1 Byte
Sub-Res X, Byte Count
1 Byte (NxN
0
+1)
Sub-Req X, File Number
2 Bytes
Sub-Res X, Reference Type (0x06)
1 Byte
Sub-Req X, Start Address
2 Bytes
Sub-Res X, Register Data
NxN
0
Bytes
Sub-Req X, Register Count
2 Bytes
Sub-Res X+1……
Sub-Req X+1……
Error Check (CRC)
2 Byte
Error Check (CRC)
2 Bytes
Notes:
1)
Modbus function code 0x14 is used to access the Data Recorder Log, Energy Log and Waveform
Recorder Log.
2)
Start Address = [
Log #X Pointer
/
Log #X Depth
].
3)
In the Request Packet, the
File Number
parameter is used to reference which log to read:
a)
For Data Recorder Logs 1 to 16,
File Number
= 1 to 16
b)
For Energy Log,
File Number
= 17
c)
For Waveform Recorder Log,
File Number
= 18 to 23
4)
In the Response Packet,
N
represents the number of logs returned, and
N
0
is the length of a single
log:
a)
For Data Recorder,
N
0
= n*4+8 where n is the number of parameters for a particular Data
Recorder
b)
For Energy Log,
N
0
= n*4+8 where n is the number of parameters for the Energy Log
c)
For Waveform Recorder Log,
N
0
= 2
