Lantronix EDS2100 EDS1100 / EDS2100 - User Guide - Page 97

: Modbus, Serial Transmission Mode

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12: Modbus Modbus ASCII/RTU based serial slave devices can be connected via the ethernet through an existing Modbus TCP/IP network. Any device having access to a given Modbus implementation will be able to perform full range of operations that the implementation supports. Modbus/TCP use a reserved TCP port of 502 and include a single byte function code (1=255) preceded by a 6 byte header: Table 12-1 6 Byte Header of Modbus Application Protocol Transaction ID (2 bytes) Identification of request/response transaction - copied by slave Protocol ID (2 bytes) 0 - Modbus protocol Length (2 bytes) Address (1 byte) Number of following bytes includes the unit identifier Identification of remove slave Serial Transmission Mode Evolution products can be set up to communicate on standard Modbus networks using either RTU or ASCII. Users select the desired mode and serial port communication parameters (baud rate, parity mode, etc) during the line configuration. Table 12-2 Modbus Transmission Modes RTU  Address: 8 bits (0 to 247 decimal, 0 is used for broadcast)  Function: 8 bits (1 to 255, 0 is not valid)  Data: N X 8 bits (N=0 to 252 bytes)  CRC Check: 16 bits ASCII  Address: 2 CHARS  Function: 2 CHARS  Data: N CHARS (N=0 to 252 CHARS)  LRC Check: 2 CHARS The Modbus web pages allow you to check Modbus status and make configuration changes. This chapter contains the following sections:  Modbus Statistics  Modbus Configuration EDS1100/2100 User Guide 97

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EDS1100/2100 User Guide
97
12: Modbus
Modbus ASCII/RTU based serial slave devices can be connected via the ethernet through an
existing Modbus TCP/IP network.
Any device having access to a given Modbus implementation
will be able to perform full range of operations that the implementation supports.
Modbus/TCP
use a reserved TCP port of 502 and include a single byte function code (1=255) preceded by a 6
byte header:
Table 12-1
6 Byte Header of Modbus Application Protocol
Serial Transmission Mode
Evolution products can be set up to communicate on standard Modbus networks using either RTU
or ASCII.
Users select the desired mode and serial port communication parameters (baud rate,
parity mode, etc) during the line configuration.
Table 12-2
Modbus Transmission Modes
The Modbus web pages allow you to check Modbus status and make configuration changes.
This
chapter contains the following sections:
Modbus Statistics
Modbus Configuration
Transaction ID (2 bytes)
Identification of request/response transaction - copied by slave
Protocol ID (2 bytes)
0 - Modbus protocol
Length (2 bytes)
Number of following bytes includes the unit identifier
Address (1 byte)
Identification of remove slave
RTU
ASCII
Address:
8 bits (0 to 247 decimal, 0 is used
for broadcast)
Function: 8 bits (1 to 255, 0 is not valid)
Data: N X 8 bits (N=0 to 252 bytes)
CRC Check: 16 bits
Address:
2 CHARS
Function: 2 CHARS
Data: N CHARS (N=0 to 252 CHARS)
LRC Check: 2 CHARS