Configuring interfaces to the central BMS
Modbus RTU interface
Single room control system FSL
‑
CONTROL II
69
5
Modbus function 8 (0x08) Diagnostics
This function is used to check the Modbus communication.
Request:
Byte 0 Slave Address Rotary switch 1-99
Byte 1 Function Code 0x08
Byte 2-3 Subfunction see below
Byte 4-5 Data see below
Response:
Byte 0 Slave Address Rotary switch 1-99
Byte 1 Function Code 0x08
Byte 2-3 Subfunction see below
Byte 4-5 Data see below
Error:
Byte 0 Slave Address Rotary switch 1-99
Byte 1 Error Code 0x88
Byte 2 Exception Code 0x01,0x03
Sub- Data Data Name
func. Requ. Resp. Meaning
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0 * * Return Query Data
The whole frame (100 bytes max.) is sent back.
1 x x Restart Communications Option
Modbus communication restarts after the response,
Listen Only Mode ends.
4 0 - Force Listen Only Mode
No response is sent. Listen Only Mode starts immediately.
The device reacts only to the Diagnostics function,
Restart Communications Option subfunction.
10 0 0 Clear Counters
All 5 diagnosis counters are deleted.
11 0 Count Return Bus Message Count
Request the number of error-free messages received.
12 0 Count Return Bus Communication Error Count
Number of messages with a CRC error, length < 3,
request parity error or framing error
13 0 Count Return Slave Exception Error Count
Request number of error messages.
14 0 Count Return Slave Message Count
Request number of messages for this device.
15 0 Count Return Slave No Response Count
Request number of broadcast messages.