Pepperl+Fuchs ICDM-RX/MOD Manual page 17

ICDM-RX/MOD User Manual
Overview
• Appropriate Modbus responses are returned to the Modbus master.
• Broadcast Modbus messages, those with a unit identifier of zero, are transmitted out all Modbus To-slaves
serial ports on the ICDM-RX/MOD. Depending on the remote device configuration(s), remote slave devices
may or may not receive broadcast messages.
From a message routing standpoint, all local and remote public Modbus slave devices attached to a ICDM-RX/
MOD gateway (1, 2, or 4-port) must be addressed with unique Unit Identifiers. Valid Unit Identifiers are 1 to 255
and the Broadcast Identifier is zero. However, the Device ID Offset functionality can be configured to change
the addressing of serial connected slave devices to allow multiple slave devices with the same unit ID to be
connected to the same gateway, but addressed differently. For more information, see section on Alias and
Device ID Offset functionality.
To communicate to local Modbus slave device(s) through a ICDM-RX/MOD, perform the following steps.
1. Select the Serial menu and then select the appropriate port.
2. Under Serial Configuration, configure the serial port parameters such as the Mode, Baud rate, Data Bits,
and so forth.
3. Under Modbus Settings, set the Serial Port Protocol to Modbus/RTU-To-Slaves or Modbus/ASCII-To-
Slaves.
4. Under Modbus Slaves To-Slaves Settings, set the Response Timeout to the desired value.
Note: 2- and 4-Port only: Set the Lost Device Search Enable setting. See Local Public Modbus Slave
Device Search Methodology.(below) for more information.
5. If desired, configure the Device ID Offset Mode and Device ID Offset.
To communicate to remote Modbus slave device(s) through a ICDM-RX/MOD, perform the following steps.
1. Select the Modbus menu and then the Remote Modbus Configuration page.
2. Click the Add Remote Configuration button.
3. Configure each remote device as needed and click Save.
To enable the Alias Device ID capability for one or more device Ids, perform the following steps.
1. Select the Modbus menu and then the Alias Configuration page.
2. Click the Add Alias Configuration button.
3. Configure each alias device ID as needed and click Save.
1.6.2. Local Public Modbus Slave Device Search Methodology
Locating a local Modbus slave device on a ICDM-RX/MOD 1-port is relatively simple. Either the Modbus slave
device is connected to the port or it is not. However, if more than one port is configured for Modbus To-Slaves
on a ICDM-RX/MOD 2- or 4-port, the device must be found. The following is an explanation of how the search
algorithm works on a ICDM-RX/MOD 2- or 4-port.
Locating a Local Modbus slave device after a reboot or port reset: When the ICDM-RX/MOD receives a
message for a public Modbus slave device for the first time since reboot or port initialization, it will transmit the
Modbus message out all Modbus To-Slaves serial ports and wait for a response to be returned. Once the
response is returned, the device port is known and all messages sent to the device will be routed through the
serial port.
Lost Devices: Lost devices, or devices that time out, are a special case. The ICDM-RX/MOD provides two
methods for handling lost devices via the Lost Device Search Enable option on the web page.
• Disabling this option on a Modbus To-Slaves port:
- Prevents the ICDM-RX/MOD from searching for a lost device on other Modbus To-Slaves ports.
- Prevents lost devices known to have been on other ports from being searched for on this port.
Note: This is the recommended setting whenever it is desired to prevent timeout delays on other Modbus
To-Slaves ports in the event that a device times out.
• Enabling this option on a Modbus To-Slaves port:
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