ELPRO 805U-E Uživatelský manuál stáhnout pdf (Strana 45)

Chapter Three Operation

Page 45 © April 2007

3.12.3 Modbus TCP to RTU Server

The Modbus TCP to RTU Server allows an Ethernet Modbus/TCP Client (Master) to

communicate with a serial Modbus RTU Slave. The 805U-E makes this possible by

internally performing the necessary protocol conversion. The conversion is always performed

by the 805U-E which is directly connected to the Modbus serial device (i.e. only this module

needs to have Modbus TCP to RTU Server enabled).

The above example demonstrates how a Modbus/TCP Client (Master) can connect to one or

more Modbus RTU (i.e serial) Slaves. In this example the 805U-E Access Point is configured

with the “RS232 Modbus/TCP to RTU Gateway” enabled. Once enabled, the gateway

converts the Modbus/TCP queries received from the Master into Modbus RTU queries and

forwards these over the RS232 port to the Slave. When the serial response to the query

arrives from the Slave, it is converted to a Modbus/TCP response and forwarded via the

network to the Modbus/TCP Master. If no response was received serially by the 805U-E

within the configured Response Timeout, the 805U-E will initiate a number of retries

specified by the configured Maximum Request Retries.

The Modbus TCP to RTU Server may be configured to operate on either the RS-232 or

RS-485 port. It does not support operation on both ports at the same time.

Enable RS-232 Modbus

TCP to RTU Gateway

Check this box to enable the Modbus TCP to RTU Server on the RS-232

port. Only a single serial port is allowed at a time.

Enable RS-485 Modbus

TCP to RTU Gateway

Check this box to enable the Modbus TCP to RTU Server on the RS-485

port. Only a single serial port is allowed at a time.

Data Rate The serial data rate desired. Serial data rates available range from 110bps

to a maximum of 38,400bps.

Data Bits Parity Stop Bits The data format desired. Data formats of 8N1, 7E1, 7O1, 7E2, 7O2 are

supported.

Pause Between Requests Enter the delay between serial request retries in milliseconds

Response Timeout Enter the serial response timeout in milliseconds – a serial retry will be

sent if a response is not received within this timeout.

Connection Timeout Enter the TCP connection timeout in seconds – if no Modbus/TCP data

is received within this timeout then the TCP connection will be dropped.

Set this field to zero for no timeout.

Maximum Request Retries Enter the maximum number of request retries performed serially.

Maximum Connections Enter the maximum number of simultaneous TCP connections to the

server allowed.

Client

LAN

Modbus/TCP Client

(Master)

RS232

Modbus RTU

Slave

RS232

Modbus/TCP to

RTU Server

Access

Point

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