4 Modbus/TCP
4-2
Ethernet Option Board /
700.002 735 AE01
4.1
MODBUS/TCP vs. MODBUS RTU
Compared to the MODBUS RTU protocol, the MODBUS/TCP differs mostly in error checking and slave
addresses. As the TCP already includes an efficient error checking function, the MODBUS/TCP protocol does
not include a separate CRC field. In addition to the error checking functionality, the TCP is responsible for
resending packets and for splitting long messages so that they fit the TCP frames.
The slave address field of the MODBUS/RTU is named as the unit identifier field in MODBUS/TCP, and it is
only used when one IP address stands for several endpoints.
4.2
Ethernet Option Board's Modbus Addresses
A Modbus/TCP class 1 functionality has been implemented in OPT-CI board. The following table lists
supported MODBUS registers.
Name
Size
Modbus address
Type
Input Registers
16bit
30001-3FFFF
Read
Holding Register
16bit
40001-4FFFF
Read / Write
Coils
1bit
00001-0FFFF
Read / Write
Input discretes
1bit
10001-1FFFF
Read
Table 4-1: Supported Registers
Name
Size
Modbus address
Type
Input Registers
16bit
30001-3FFFF
Read
Holding Register
16bit
40001-4FFFF
Read / Write
Coils
1bit
00001-0FFFF
Read / Write
Input discretes
1bit
10001-1FFFF
Read
Table 4-2: Supported Registers
4.3
Coil (0x01) Register
The Coil register represents data in a binary form. Thus, each coil can only be in mode “1” or mode ”0”. Coil
registers can be written using the MODBUS function 'Write coil' (5) or the MODBUS function 'Force multiple
coils' (16). The following tables include examples of both functions.
4.3.1
0001 –00016 Control Word (Read / Write)
Address
Function
Purpose
0001
RUN/STOP
Control word, bit 1
0002
DIRECTION
Control word, bit 2
0003
Fault reset
Control word, bit 3
0004
FBDIN1
Control word, bit 4
0005
FBDIN2
Control word, bit 5
0006
FBDIN3
Control word, bit 6
0007
FBDIN4
Control word, bit 7
0008
FBDIN5
Control word, bit 8
0009
BusCtrl
Control word, bit 9
0010
BusRef
Control word, bit 10
0011
FBDIN6
Control word, bit 11
0012
FBDIN7
Control word, bit 12
0013
FBDIN8
Control word, bit 13
0014
FBDIN9
Control word, bit 14
0015
FBDIN10
Control word, bit 15
0016
FBFaultIN
Control word, bit 16
Table 4-3: Control Word Structure
Summary of Contents for 700.002 735
Page 1: ...Ethernet Option Board LV7000 Order No 700 002 735 Issue 06 08 AE01 Operating Manual ...
Page 8: ...Contents Ethernet Option Board 700 002 735 AE01 ...
Page 10: ...1 Introduction 1 2 Ethernet Option Board 700 002 735 AE01 ...
Page 14: ...2 Ethernet Board Technical Data 2 4 Ethernet Option Board 700 002 735 AE01 ...
Page 20: ...3 Installation 3 6 Ethernet Option Board 700 002 735 AE01 ...
Page 30: ...4 Modbus TCP 4 10 Ethernet Option Board 700 002 735 AE01 ...
Page 32: ...5 Start up Test 5 2 Ethernet Option Board 700 002 735 AE01 ...
Page 34: ...6 Error Codes and Errors 6 2 Ethernet Option Board 700 002 735 AE01 ...
Page 37: ......
