Network Card User Manual

MODBUS REGISTERS

EATON Power Xpert

Gateway Series 1000 Card User’s Guide S 164201670 Rev 1

Modbus Register Addressing

This section describes Modbus function codes, data formats, and data

addressing.

Modbus Function Codes

The PDU/RPP registers are read using Modbus Function Codes (FC). For

most PDU/RPP registers, FC 04 is used. The PDU/RPP supports the

following hex function codes:

Table 1. Function Codes

FC Hex Description Use

01 0x01 Read Coil Status Supported for compatibility purposes

02 0x02 Read Discrete Inputs Single input data, such as alarms and

discrete contacts

03 0x03 Read Holding Registers Supported for compatibility purposes

04 0x04 Read Input Registers Analog data (most string and numeric

data types), such as voltage

05 0x05 Write Single Coil For future use

06 0x06 Write Single Register For future use

0F 0x0F Write Multiple Coils For future use

10 0x10 Write Multiple Registers For future use

Data Formats

Modbus programs usually provide an option for viewing various data

types. Refer to your Modbus program documentation for detailed

information on viewing data options.

A register is 16 bits (two bytes). The PDU/RPP supports the following

data types:

S STRING – A string of ASCII characters (two per register). Consult the

Size parameter to find the string’s length for a given entry (it is a

multiple of two so that entries are register-aligned).

S FLOAT – A 32-bit IEEE754 floating point number. FLOATs are always

two registers.

S UINT – An unsigned integer. Consult the Size parameter to find the

integer’s size for a given entry (it is a multiple of two so that entries

are register-aligned).