Operation If an Error Occurs
FP2 Serial Data Unit
6 − 5
6.2 What To Do If An Error Occurs
6.2 What To Do If An Error Occurs
6.2.1 If the ALARM LED Lights on the Serial Data Unit
Situation
The watchdog timer is activated to alert the user of a problem with the serial data unit.
Solution
Turn the power supply off and then on again.
If the LED lights again, there may be a problem with the unit.
If the LED goes out after the power supply is turned off and then on again, the problem
may have been caused by noise or another temporary phenomenon. Continue operation
and watch for further signs of trouble.
6.2.2 If the ERROR LED on the Serial Data Unit Lights
Situation
A parity error, a framing error, an overrun error, or a BCC error has occurred.
Solution
Confirm the status of the I/O contacts listed below in the serial data unit using the
programming tool.
With the serial data unit, the ERROR LED goes out when correct data is sent or received.
Contents of error and flags
Applicable port Contents and solution
COM1 COM2
X4 X9 A “framing error” has occurred. This occurs when the data length or stop bit of the received
data is different from the settings that have been entered. Check the data length and stop bit
settings.
X5 XA A “parity error” has occurred. This occurs when the parity of the received data is different
from the setting that has been entered. Check the parity setting.
X6 XB A “buffer full error” has occurred. This occurs when the received buffer is full. Interrupt the
sending of data from the RS232C device on the other end.
X7 XC This is a “received message length error” that occurs when the frame length of the received
data exceeds 500 bytes. Check to see if the end code of the received data matches that on
the unit side, or set the frame length for the received data to 500 bytes or less.
X8 XD This is a “sent message length error” that occurs when the frame length of the sent data ex-
ceeds 500 bytes. It occurs if there is no end code in the sent data. Check to see if the sent
data contains an end code, or set the frame length for the sent data to 500 bytes or less.
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