6.5.3 Exception codes
The Modbus function 23 communication protocol
implements five default Modbus Exception Codes for
incorrectly entered values.
The table below describes the corresponding errors
and proposes their solutions.
Code Error Solution
01 The function code is wrong Enter the Function 23 code: 0x17
02 Wrong Read starting address. Enter Read Starting Address: 0
Wrong Write starting address. Enter Write Starting Address: 0 or 1
03 Wrong Quantity to Read. Enter Quantity to Read: 6
Wrong Quantity to Write. Enter Quantity to Write: 6
04 Packet size is too large or too small. Enter a Packet sized exactly 25 bytes,
including Modbus ID + CRC.
IDAL value is too high Enter a maximum 5 bit value.
IDB value is too high Enter a maximum 18 bit value.
05 The time out error occurs when there is
no response from MasterBus for three
seconds.
Check if the MasterBus powering device is working and/or
check the MasterBus wiring.
6.5.4 Exception message
Below, the exception message is described and an example is shown.
Exception message
Variable Size Value
Bus address 1 Byte Variable
Function code 1 Byte 0x97 (Fixed)
Exception code 1 Byte Variable
CRC 2 Byte Calculated
Exception message example
Variable Value Range
Bus address 0x01 [1..247]
Function code 0x97 Fixed
Exception code 0x05 [1..5]
CRC Lo 0x8E
[0..255]
CRC Hi 0x33
[0..255]
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