Modbus TCP
5.3 Function codes, metering values and parameters
3WA Air Circuit Breaker Communication
36 System Manual, 11/2021, 92310000004-02
5.3 Function codes, metering values and parameters
5.3.1 Function codes
The COM190 communication module supports the following Modbus function codes:
• 0x03 – Read values and parameters
• 0x06 – Write single register parameters and commands
• 0x10 – Write parameters and commands
• 0x2B – Device identification
5.3.2 Metering values, parameters and commands
5.3.2.1 Reading metering values and parameters
Modbus function code 03 (hex: 0x03) reads values and parameters out of the 3WA circuit
breaker. The following requirements must be met for this purpose:
• The request must refer to the start address of a valid data point.
• The number of registers that are read must correspond as least to the length of the data
point to be read.
It is possible to read multiple data points with one frame. Provided the start address of the
frame refers to the start of a valid data point, reading is also possible across gaps in the
Modbus register map. Data points following the first data point may also be partially read.
Gaps or partially read data points are filled with a bit pattern for invalid values in the response
frame, see Chapter Invalid values (Page 39).
Parameters are identified as such in the Modbus register m
ap.
5.3.2.2 Writing parameters
Modbus function code 16 (hex: 0x10) writes parameters of the 3WA air circuit breaker.
Parameters with a length of one register can also be written using Modbus function
code 06 (hex: 0x06).
The following rules must be observed for a valid frame:
• The start address of the frame must refer to the start of a parameter.
• The parameter must be written in full.
• The parameter must exist in the concrete 3WA system.
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