eWON General Reference Guide - eWON wiki

General Reference Guide eWON Configuration
• Historical and real-time logging:
Those fields display only for some eWON's versions (c.f. "Tags monitoring and handling" on page 76)
Historical logging enabled
3.4.2.1.1 Publish as Modbus TCP
This feature allows to access a Tag Value through Modbus/TCP. In that configuration, the eWON acts as a slave. Actually, there is no data map
as in most PLC, instead of that you define Tag by Tag its Modbus TCP address.
3.4.2.1.1.1 Defining the Modbus TCP address
There are 4 types of Modbus variable, Contact (RO), Coil (RW), Input Register (RO), Holding register (RW). The type selected for the Tag that
you want to publish will depend on its type:
Usually, the RO or RW property of a Tag is obvious. But in case of doubt, you can confirm the type by checking the View IO for the Tag:
• Remove the "Force Read Only" option in the Tag configuration (disabled by default).
• Check the View IO page, if the Tag has an update field, it means it is a RW Tag otherwise the Tag is RO.
• The address selected will be the address of the Modbus 16 bit register. The address range starts with register 1 (in the Modbus frame,
eWON register 1 is transmitted as 0).
• Publish as float
The eWON supports accessing Tag values as float registers. The float is published with the IEEE representation and the value can be read on 2
consecutive registers, with the first register starting at the user defined address.
3.4.2.1.1.2 Modbus TCP rules
Historical and real-time logging
If checked, the Tag values will be logged in a circular file.
Warning: This is a non-volatile logging; data are stored in the flash file system. All the data are stored in
the same file, the maximum number of values that can be saved is from 16384 to 139264, depending on
the way you have set up the resources storage in the eWON (when maximum size is reached, then the
older data will be erased first).
If one Tag "a" is recorded very often (every seconds) and another Tag "b" is recorded rarely (every day),
you may have your Historical Log filled with a lot of tag "a" and few (or none) tag "b" because of the
circular storage mechanism.
Logging dead band Defines the dead band of the Tag’s incremental recording (use a negative value to disable it)
Logging Interval
Real time enabled
Defines the interval, in seconds, for the Tag recording (set to zero to disable the logging interval).
Can be used at the same time as logging dead band.
If checked, the Tag values will be logged in memory.
Real time logging is different from historical logging because data are saved in a circular memory buffer.
The other difference with historical time logging is that incremental recording is not possible, only fixed
interval recording can be performed.
Time span Defines the total logging window time in seconds.
Logging Interval Defines the interval, in seconds, of the Tag recording
Table 54: Historical and real-time logging controls
Tag property Modbus data type
Boolean, RO Contact
Boolean, RW Coil
Analog, RO Input register
Analog, RW Holding register
Table 55: the 4 Modbus variable types
• When accessing Modbus registers or coils that are not mapped to an eWON register, the returned value is 0.
• Maximum number of registers readable in 1 request: 25
• Maximum number of coils readable in 1 request: 2000
RG-001-0-EN ver 1.14 eWON® - 02/05/2012 - ©eWON sa Page 82