Honeywell UDC2500 - Manual (Page 194)

Modbus RTU Function Codes
180 UDC2500 Universal Digital Controller Product Manual 4/07
9 Modbus RTU Function Codes
9.1 Overview
This section describes the function codes needed to upload and download the
configuration from a host computer into this instrument.
What's in this section?
The following topics are covered in this section.
TOPIC See Page
9.1 Overview 180
9.2 General Information 180
9.3 Function Code 20 182
9.4 Function Code 21 186
9.2 General Information
This instrument uses a subset of the standard Modbus RTU function codes to provide
access to process-related information. Several MODICON function codes are
implemented. It is appropriate to define instrument-specific "user-defined" function
codes. Where differences occur between the two protocols it will be noted. Several
standard Modbus RTU function codes are supported.
Configuration ID Tags
Function codes 20 and 21 use the RS422/485 tag IDs for accessing configuration and
process-related data. These tags are fully explained in Section 10.
The tag IDs represent the register addresses used in the Request Message.
Other Modbus Codes
For Modbus codes other than for accessing configuration and process-related data for
this controller, refer to the Modbus RTU Serial Communications User Manual # 51-55-
25-66.