Yokogawa PR300 Power and Energy Meter - Manual (Page 87)

5-8
<Toc> <Ind> <5. Modbus/RTU and ASCII Communication Protocols>
IM 77C01E01-10E
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Responses to Abnormal Messages
If there is any failure other than transmission errors, the PR300 returns the following re-
sponse message without executing any process:
Element
Number of bytes in RTU mode
Number of bytes in ASCII mode
None
1
1
2
1
2
1
2
2
2
Start of
Message
Mark (:)
Station
Number
(ST-NO)
Function
Code
( * 1)
Error
Code Error
Check
[CR][LF]
None
2
*1: The function code entered here is the function code (in hex) plus 80 (in hex).
The following table summarizes details on the error codes.
Meaning
Funcation code error
Abnormal number of D registers
Error Code
01
03
02 Abnormal D register number
Cause
Function code does not exist.
Number of D registers out of the range is specified.
D register number out of the range is specified.
The PR300 does not regard it as an error even if there is any unused register among those
with consecutive register numbers specified by a readout function; rather, the PR300
returns a value of 0 in this case.
The PR300 returns the error code 02 or 03 if the specified consecutive registers are made
to fall outside the given range by the number of registers specified, even though the D-
register start number was initially within the range. (Depend on the function code.)
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Cases when There Are No Responses to Transmitted Messages
• A transmission error (overrun, framing, parity, LRC or CRC-16 error) is encountered.
• The station number in the command message is wrong.
• The interval between data composing a message is longer than 2 seconds.
• The station number is “00” (broadcast specification).
• The receiving buffer has overflowed.
Note: As a measure against the abovementioned problems, add a time-out process to the communication function or
program of the higher-level device.