Modbus
5.1 Data Format
5-5
■ Error Codes
● No Response
In the following cases, the received command will not be processed and
a response will not be returned.
Consequently, a timeout error will occur at the host device.
• The slave address in the received command does not match the
communications unit number.
• A parity error, framing error, or overrun error occurred due to a problem
such as a transfer error.
• A CRC-16 code error occurred in the received command frame.
• There was a time interval of more than 3.5 character times between
data packets that make up the command frame.
Furthermore, the specified function’s processing will be performed but
no response will be returned for broadcast functions (slave address =
H’00).
End
code
Name Description
Error
detection
priority
H'01 Function code error An unsupported function code was received. 1
H'02 Variable address error The specified variable area address is out-of-range. 2
H'03 Variable data error The amount of data does not match the number of elements.
The byte count is not 2 times the number of elements.
The response length exceeds the size of the communica-
tions buffer.
The command code or related information in the operation
command is wrong or the write data is not in the setting
range.
3
H'04 Operation error The write data contents are not allowed in the present oper-
ation mode.
◆ The Communications Writing parameter is set to “OFF”
(disabled).
◆ Attempted to write to a parameter in setup area 1 from
setup area 0.
◆ Attempted to write to a protect parameter from other than
the protect level.
◆ AT execution in progress
◆ The command cannot be processed.
4
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