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OMMUNICATION
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OMMUNICATION
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ANUAL
FC9Y-B1730
Modbus TCP Communication Request Table
A maximum of 255 requests can be configured in the Modbus TCP Client Request Table.
Notes:
•
10 bytes of the user program area are needed per each request.
•
Request execution devices and error status data registers are allocated in the order of request numbers. When deleting a request or changing
the order of requests, the relationship of the request to the request execution devices and error status data register is changed. If the
allocated internal relays or data registers are used in the user program, those device addresses must be updated accordingly.
Use a single DR for all
communication requests
Error data of each communication request
Unchecked
Error data, the remote host number (high-order byte) and error code (low-order byte), of each request in the
entire request table can be confirmed. Data registers as many as the quantity of requests are reserved for
storing error data. When an error occurs for a request, error data is stored to the corresponding data register.
Checked
A single data register is shared by all requests. When an error occurs for a request, error data is stored to the
data register and the old error data is overwritten.
Bit Allocation
Remote Host Number
(high-order byte)
1 to 255
Error Code
(low-order byte)
00h: Normal completion
01h: Function code error (unsupported function code)
02h: Access destination error (address out of range, device quantity out of range)
03h: Device quantity error, 1-bit write data error (specified device quantity of 1-bit write is unsupported)
12h: Frame length error (frame length of transmitted request exceeds range)
13h: BCC error (BCC does not match)
14h: Slave number error (received slave number is invalid)
16h: Timeout error (timeout occurs)