Function Code 20 (14H) - Read Configuration Reference Data; Request And Response Formats; Byte Count; Data Byte Count - Honeywell UDC2800 Product Manual

Chapter 11 - Modbus RTU Function Codes 20&21
Function Code 20 (14h) - Read Configuration
Reference Data
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Function code 20 (14 Hex) is used in this instrument to read
information stored in its configuration database. Each configuration
item is explicitly addressed by a file number and register address.
IEEE 32-bit floating point and 16-bit integer formats are supported.

Request and Response Formats

The Request and Response formats for Function code 20 (14 Hex)
are shown below. Details for each block reference follow.
Request Message Format
Response Message Format

Byte Count

The Byte Count equals the number of bytes transmitted in either the
request or response message and will be the minimum number
required to transmit all requested data.

Data Byte Count

The Data Byte Count is the number of data bytes of the sub response
including the Reference Type but not including itself. A floating point
sub response has four bytes of data and one byte representing the
reference type making the data byte count equal to five.