SMAR DFI302, User Manual

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DFI302 – User’s Manual
11.16
Procedure to convert FF parameter to Modbus variable:
Load INx_VALUE.
Calculate Y = (A * INx B).
Convert Y to DATA_TYPE_IN, generating MOD_VAR_IN.
Write MOD_VAR_IN.
Procedure to convert Modbus variable to FF parameter:
Read MOD_VAR_OUT.
Convert MOD_VAR_OUT to float, generating Y
Calculate OUTx_VALUE = (A * Y + B).
Store OUTx_VALUE.
A = (To_EU_100% - To_EU_0%)/(From_EU_100% - From_EU_0%)
B = To_EU_0% - A*From_EU_0%;
from_EU_0%
To_EU_0%
To_EU_100%
from_EU_100%
X
Y
IN_VALUE, OUT_VALUE: FF parameters
MOD_VAR_IN, MOD_VAR_OUT: Modbus variables
Y: auxiliary float variable
Setting the Inputs and Outputs of the MBCM block
To read a Modbus variable, connect it to an output of the MBCM function block. To write in a
Modbus register, connect it to an input of the MBCM block.
The Modbus protocol specifies the division of the address range to the variables.
•
00001 to 09999
Æ
Digital Outputs.
•
10001 to 19999
Æ
Digital Inputs.
•
30001 to 39999
Æ
Analog Inputs.
•
40001 to 49999
Æ
Analog Outputs.
Once the variables are mapped, defined and referenced in the MBCM block, it is possible to set the
strategy.
The variables can be connected to other FIELDBUS function blocks (Connect the output or input of
the block to blocks in the strategy), write in MODBUS registers (Connect the Input of the MBCM
block to a MODBUS register). Exchange data between two slaves (set the input of the MBCM block
with the slave address and specific MODBUS address where the value will be written and set the
output of the MBCM block with the slave address and MODBUS address of the variable where the
value will be read). This last application is showed below: