User`s manual

124

(12)An example of what to do on the programmable controller CPU side for

improper access from the external device

The following is an example of performing, on the programmable controller CPU side, the line disconnect

processing with respect to the opposite device and prohibiting receive via a modem when the number of "remote

password mismatch" detected by the Q series C24 remote password check function exceeds the number set by

the user.

• The user should determine the count and accumulated count of notification given when a remote password

mismatch occurs during the unlock processing from the external device with respect to the remote password

set in the QCPU. ( Page 116, Section 3.3.6 (3) (a),  Page 116, Section 3.3.6 (3) (b))

• In the GX Configurator-SC system settings, in order for the Q series C24 to operate, set the count

determined above in the following item on the "Modem function system setting" screen and register this to

the Q series C24.

• Set in the item "Remote password mismatch notification count."

• Set in the item "Remote password mismatch notification accumulated count."

• In addition to initialization commands used in normal modem initialization, specify "No automatic receive"

and additionally register the modem initialization command for this step to the Q series C24. (No automatic

receive: This is the setting to prohibit line connection from the opposite device.) Use the "Modem function

initialization data" screen to set.

• Constantly monitor the rise (OFF  ON) of the ERR occurrence signal (XE or XF) when connecting the line

to the opposite device using the modem function after the system begins operating.

• Monitor the following buffer memory when the ERR occurrence signal turns ON.

• Storage area for MC protocol transmission error codes (address: 602 (25AH))

• Perform the line disconnect processing with respect to the opposite device when the error code stored in the

above buffer memory is 7FE8H. (Use the modem disconnection request signal (Y12).)

• After the above line disconnect processing is completed, specify the modem initialization command for which

"No automatic receive" has been specified and perform modem initialization only. ( Page 154, Section

3.4.7)

• Describe the above occurrence to the system manager and take necessary measures.