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Siemens RWD Primary Controls Modbus Interface CB1P3099en_01

Building Technologies Modbus Operation 27.10.2009

4 Modbus Operation

The valid Function Codes are as follows:

Function

Code (Hex)

Data

Length

Functions

RWD Parameter

Addressable

Ranges

0x01

1 Read R/W Flag (Coil)

0x05

1 Write R/W Flag (Coil)

0xxxx

e.g. 00001, 00003

0x02

1 Read R-only Flag (Discrete Input)

1xxxx

e.g. 10004

0x03

2 Read R/W Register (Holding Register)

0x10

2 Write R/W Register

4xxxx

e.g. 40109, 40111

0x04

2 Read R-only Register (Input Register)

3xxxx

e.g. 30001, 30007

The following examples will illustrate how users can construct Modbus messages with

all available function codes above and the returned messages from the RWD via

SEZ50MB. (To interpret the meanings of the returned messages, please refer to the

next section RWD Parameters & Addresses).

Read RWD32S parameter (ADDR = 00001) called “bFrostEnable” with Modbus ADDR

= 0000:

SEZ50MB

Device

Address

Function

Code

Modbus Address Data Length CRC16

Check

Send

F7 01 00 00 00 01 E9 5C

SEZ50MB

Device

Address

Function

Code

Byte

Count

Status CRC16

Check

Respond

F7 01 01 01

(bFrostEnable = Enable)

A3 C0

Read RWD68 parameter (ADDR = 10005) called “Q1_output” with Modbus ADDR =

0004:

SEZ50MB

Device

Address

Function

Code

Modbus Address Data Length CRC16

Check

Send

F7 02 00 04 00 01 EC 9D

SEZ50MB

Device

Address

Function

Code

Byte

Count

Status CRC16

Check

Respond

F7 02 01 00

(Q1_output = Off)

92 00

Modbus Function Codes

Examples Of Using

Different Modbus

Function Codes

Function Code 0x01 à

Function Code 0x02 à