Modbus Error Reponse - Bell VFM60 Series User Introduction Manual

registers come first.
eg: 100=0x00,0x00,0x42,0xc8
-100=0x00,0x00,0xc2,0xc8
4: HL_HH_LL_LH the higher 16 bytes registers come first, the lower 8 bytes within the 16 bytes
registers come first.
eg: 100=0xc8,0x42,0x00,0x00
-100=0xc8,0xc2,0x00,0x00

6.6 Modbus error reponse

When the host sends a command and asks for a correct reponse, one of below three is going to
happe:
1) If the command from the host is correct and processable, the flow meter will give a correct reponse.
2) If the flowmeter received a command, but detected parity, the error of LRC and CRC will cause no
reponse. The host will process a overtime commend.
3) If the flowmeter recived a correct command, but can not process it (read or write a none-existing
register etc.), the flowmeter will send a error reponse
A error reponse has two byte sections to show its difference from a correct reponse.
Function code section: In a correct reponse, the flowmeter will copy the origin function code sent from
the host, and the highest bytes of them are all 0(all function codes are smaller than 0x80). In a error
reponse, the flowmeter will set the highest bytes to 1. The host can detect the error code and know the
content of the error when it detect that the highest bytes of function codes are 1.
Value section: In a error reponse, the flowmeter will reply a byte as the error code to definite the
content of the error. Pleaes reference to the chart below for the error codes and its definition:
Code Name
01 Illegal function
code
02 Illegal address
03 Illegal contents
of value
04 Flow meter
function failed
Date:24/04/2020
Meaning
Flowmeter can not process the function code in a command. Maybe
this function code can only be used on a new device, or it can also
indicate that the flowmeter is under error statues.
The flowmeter can not process with the address in the command. The
initiate address plus address diversion are higher than the highest
address.
The content of the value in the command is not acceptable for the
flowmeter.
An unrecoverable failure happened when the flowmeter is trying to
reponse.
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VFM-60
Vortex Flowmeter
Rev1.3
User's Manual