Additional Global Parameters

The following global variables will supersede default values and the values defined in the .ini file unless otherwise noted:

Writing Single Coils

Some devices use the Force Single Coil command (function code 5) for writing single coils.

Other devices support (sometimes exclusively) the Force Multiple Coils (function code 15) when writing coils. 

You can configure the Modbus Ethernet communication interface to use a specific function code when writing single coils and when interacting with a particular device. 

DeviceId_ ONE_COIL_WRITE

For Project
Purpose To control the behavior, for writing single coils on a specific device
Value Y Will cause function code 5 to be used.
N Will cause function code 15 to be used.
Comment For device models Modicon 484, VersaMax ENIU and VersaPoint ENIUs, single coils writes will be selected regardless of the user-configured preferences.

Writing Single Holding Registers

Some devices use the Force Single Holding Registers command (function code 6) to write a single holding register.

Other devices support (sometimes exclusively) the Force Multiple Holding Registers Command (Function Code 16). 

DeviceId_ ONE_REG_WRITE

For Project
Purpose To control the behavior, for writing single holding registers on a specific device
Value Y Will cause function code 6 to be used.
N Will cause function code 16 to be used.
Comment For device models Modicon 484, VersaMax ENIU and VersaPoint ENIUs, when performing a request to write a single register, single register writes will be selected regardless of the user configured preferences.

Connection Conservation

Some devices will terminate a connection if there is no activity for some pre-configured interval. 

DeviceId _CONSERVES_CONN

For Project
Purpose: To re-define how the device communication interface handles a disconnect as it relates to device down for some devices that terminate a connection if there is no activity for some pre-configured interval. 
Value: Y The device will not be declared down unless it is unable to re-establish the connection and perform the next immediate I/O operation to request or modify data on the device.  
Comment For device model VersaPoint ENIU, the device communication interface will perform specific processing that overrides the behavior of this setting. 

Host Redundancy with Devices with One Connection

Some devices will support only one connection.

In host redundant environments, it is necessary to identify the devices with this characteristic so that the connection can be terminated on the acting secondary and initiated on the primary following a transition in the host redundancy roles.

Note that a device down will not be generated as a result of not having a connection with the secondary. To identify a device that supports only a single connection, define the following project level global parameter.

DeviceId_CONN_SECONDARY

For Project
Purpose To identify a device that supports only a single connection. 
Value N