Basic Documentation

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Siemens RWD Primary Controls Modbus Interface CB1P3099en_01
Building Technologies Modbus Operation 27.10.2009
Whenever an unexpected message is received or an error is encountered by SEZ50MB,
the SEZ50MB would return a RESPOND for such errors. Modbus communicaton frame
contains an error field for exception codes, which can be used by network application to
determine what appropriated action will be taken.
Exception Code (Hex) Function Code Descriptions
0x01 Illegal Function Code
0x02 Modbus ID Check Error
0x03 Range Check Error
0x04 RWD is Lost
0x06 SEZ50MB is Busy
0x07 Gateway Device Lost
0x14 Wrong Setting For Quantity of Items In Modbus Frame
The same examples for the constructing Function Codes are used but errors are added
to illustrate how SEZ50MB responses and handles abnormal situation by returning a
message containing exception codes to the users.
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 00 E9 5C
↑ WRONG INFO
SEZ50MB
Device
Address
Function
Code
Exception Code CRC16
Check
Respond
F7 81 14 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 00 EC 9D
↑ WRONG INFO
SEZ50MB
Device
Address
Function
Code
Exception Code CRC16
Check
Respond
F7 82 14 2D 5D
Read RWD68 parameter (ADDR = 40117, 40118) called “SP3day” with Modbus ADDR
= 0116, 0117:
SEZ50MB
Device
Address
Function
Code
Modbus Address Data Length CRC16 Check
Send
F7 03 00 74 00 00 or 01 D0 86
↑ WRONG INFO
SEZ50MB
Device
Address
Function
Code
Exception Code CRC16 Check
Respond
F7 83 14 A1 0D
Exception Codes
Examples Of Errors
Function Code 0x01 à
(Error Message)
Function Code 0x02 à
(Error Message)
Function Code 0x03 à
(Error Message)