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4 Modbus Communications Procedure
E5
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C-T Digital Temperature Controllers Programmable Type Communications Manual (H186)
4-1 D
ata F
o
rmat
4
4-1-3 Error C
odes
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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).
4-1-3 Error Codes
End code Name Description
H'01 Function code
error An unsupported function code was received.
H'02 Variable address
error The specified variable area address is out-of-range.
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 communications buffer.
The command code or related information in the operation command is wrong or
the write data is not in the setting range.
H'04 Operation error The write data contents are not allowed in the present operation 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 is in progress.
• The command cannot be processed.