Process Image; Basic Version Of 750-484 I/O-Module - WAGO I/O-SYSTEM 750 Manual

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Process Image

4 Process Image
Mapping of process data in the process image of fieldbus systems
The representation of the I/O modules' process data in the process image
depends on the fieldbus coupler/controller used. Please take this information as
well as the particular design of the respective control/status bytes from the
section "Fieldbus Specific Design of the Process Data" included in the description
concerning the process image of the fieldbus coupler/controller used.
Evaluation of Status Byte
Some fieldbus systems can process status information of process value by
means of a status byte.
This status byte can be displayed via the commissioning tool WAGO-I/O-
CHECK.
However, processing via the fieldbus coupler/controller is optional, which means
that accessing or parsing the status information depends on the fieldbus system.
The HART I/O module provides the fieldbus coupler/controller with a different
amount of process data depending on the operating mode set.
4.1

Basic Version of 750-484 I/O-Module

For pure 4 mA ... 20 mA analog values the HART module transmits 16-bit
measured values and optionally 8 status bits on each channel.
The digitalized measured value is transmitted to the process image of the
coupler/controller in a data word (16 bits) as an input byte 0 (low) and input byte
1 (high).
This value is mapped with a resolution of 13 bits on Bit B2 ... B14.
Status information, which can be evaluated in the event of a fault, is contained in
the two least significant bits (B0 and B1). If the measurement is above the
measuring range, Bit B0 is set = 1, and if the measurement is below the
measuring range or if a wire breaks, Bit B0 and B1 are set = 1.
The input voltage range for the measured values of 4 mA to 20 mA is scaled to
the numerical range from 0x0000 to 0x7FFD.
Manual
Version 1.4.0
WAGO-I/O-SYSTEM 750
750-484 2AI 4-20mA HART Ex i