YOKOGAWA UTAdvanced Series, User Manual

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3-7
IM 05P07A01-01EN
Description of RS-485 Communication (for UT
Advanced with RS-485 Communication)
3
3.1.3 Configuration of Responses (response from UTAdvanced)
If the instruction message from the host computer is normal and the address is for itself,
the UTAdvanced moves to the process execution phase after it judges that the received
content is normal. The UTAdvanced then parses the content of the instruction message
and executes processing.
However, it does not execute processing if the content of the instruction message is
in error. In this case, the UTAdvanced either ignores received content, or generates a
response message to inform the host computer that the received content is in error.
After executing the requested processing when the received content is normal,
the UTAdvanced generates a response message appended with an error check
corresponding to the instruction function code, and sends this message to the host
computer.

Response in a normal state
In the case of the loopback function and write function on a single D register / I relay,
the UTAdvanced returns the same response message as the instruction message.
In the case of a write function on multiple D registers / I relays, the UTAdvanced
returns part of the instruction message as the response message.
In the case of the read function, the UTAdvanced appends the address No. and
function code with the data that was read, and returns this as the response message.

Response in an error state
When a communication error (framing error, parity error, inter-character timer timeout,
or receiving frame over-length) occurs, the UTAdvanced does not return a message.
When the message contains an inconsistency other than a communication error, the
UTAdvanced does not perform any processing, and returns the following message.
Element
Message start
mark
Address No
(ADR)
Function code
(*1)
Data Error check Message end
mark
Number of bytes in RTU mode None 1 1 1 2 None
Number of bytes in ASCII
mode
1 2 2 2 2 2
*1: The value of “ function code (Hex) + 0x80” is set in the function code.
The following shows the details of the error code.
Error code Meaning Cause
01
Function code error The function code does not exist.
02
D register / I relay No. error A No. outside the range has been specified.
03
Number of D registers / I
relays error
A number of registers outside the range has been specified.
09
Monitor not specified An attempt was made to read a monitor without specifying the monitor.
Even if continuous D registers specified by a read function include unused registers,
no error is generated and the UTAdvanced returns “0” as the value.
The UTAdvanced returns error code “02” or “03” when the start address of
continuously specified addresses is in the range, and the continuously specified
addresses become out of range as a result of the number of specified addresses
(according to function code).

When there is no response even after a message is sent:
• When a transmission error (overrun, framing, parity, LRC or CRC-16 error) is detected
• When the address in the instruction message is wrong
• When the inter-character timer timeout occurs
• When the communication address is “00” or “F9” (broadcast specification)
• When a receive buffer overflow (buffer size: 512 bytes) has occurred
Note: As a measure for the above, execute time-out processing by the communication function or
communication program on the host computer.
3.1 Modbus Communication