Eaton MTL83*C Modbus, Software Manual

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4 INM MTL83xC PC Modbus Rev 1
DRAFT - 06 January 2019
3 .3 On-line Configuration
Configuring the unit via the Modbus master and the network might seem to be the
simplest method at first sight, but there are a number of practical difficulties with this
configuration technique. This approach means that the user must deal with a number
of complex aspects which require a significant investment of the configurer’s time
before they are understood fully. A further difficulty may be a lack of the necessary
memory space within the Modbus master. If the configuration is likely to be changed
frequently it could even be necessary for the system designer to design specific ‘user
interface’ screens, such as those used by the PC software, to allow changes to be
made by operators. This would be a time consuming and costly task.
For most users, the attraction of being able to use the Modbus master to configure the
unit is that the configuration can be re-sent if the slave’s memory becomes corrupted.
Whilst this is true, it is not possible to avoid the difficulties (and costs) outlined earlier
and the decision to adopt a strategy of configuring via the Modbus master should be
arrived at only after due consideration.
A cost effective compromise would be to perform the initial configuration via the PC
software, and then read the configuration parameters stored in the MTL838C via the
host. The stored parameters could then be re-written to the MTL838C should the
configuration database ever become corrupt.
If a user intends to adopt the on-line configuration method, the calculation of
configuration parameters for storage in the master can be simplified, and the
possibility of ‘human error’ reduced, by using the PC software to input the required
data and data format, and then reading the stored values (encoded correctly in the
required data format) back from the MTL838C via Modbus. The user should still realize
that any subsequent alterations of the parameters will require further use of the PC
software.
3 .4 Off-line Configuration
Off-line configuration requires the use of the PC software briefly described below.
Once configured, the configuration parameters are stored in non-volatile memory
within the unit.
3 .5 The PC software
By far the simplest method of configuring the MTL838C is using the PC software. This
software has been specifically designed to perform all of the complex calculations that
must be carried out, in order to configure the unit. These calculations are transparent
to the user, and this method provides a convenient and time efficient method.
Alternatively, as explained before, the master could read the configured parameters
after initial off-line configuration and these may then be stored within the host for use
in the event of a database failure.