Reference to the modbus acquired tags – NOVUS Web Server – WS10 User Manual

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REFERENCE TO THE MODBUS ACQUIRED TAGS

Reference to the WS10 registers associated to external Modbus RTU devices are done through the device and tag name defined at the
MODBUS.CFG file, using one of the syntax options bellow. Only registers read with commands 3 (default command) and 1 accepts write operation.

Reference to the value of a single register

DeviceName/TagName

TT101/PV
TT101/PV.Val

Same result as above. “.Val” means the tag value and can be
omitted.

Reference to a member of a Block Register

DeviceName/TagName[n]

TT201/TVALS[0]

position of the block register

TT201/INVALS[5]

position of the block register

Reference to the status of the last read operation on a Modbus
register

DeviceName/TagName.Sts

TT101/PV.Err

TT201/TVALS[0].Err Block Register error status. The status is the same for all members

of the block

Reference to the error counter of the read operations on a
Modbus register

DeviceName/TagName.Sts

TT101/PV.ErrCnt

Number of reading errors of the register

TT201/TVALS[0].ErrCnt Number of reading errors of the block. The number is the same

for all members of the block

The values read by the WS10 from the external Modbus slaves are stored on the WS10 memory with additional status information to allow
validation of the last Modbus network operation. An communication error counter is also stored for each register.

The communication status of the last reading (.Err) is read-only and can contain the following values:

The current value was read with no error on the last scan interval.

The current value is out-dated due to a Invalid Operation error on the last scan interval.

The current value is out-dated due to a CRC error on the last scan interval.

The current value is out-dated due to a time-out error on the last scan interval.

The error counter (.ErrCnt) is a read-write value that contains the accumulated number of communication errors detected for the associated register
or block register.

The error and error counter values are not updated on write operations to the Modbus network. The WS10 doesn’t offer any function to validate the
success of a write operation into a Modbus slave.