User`s manual

3.3.3 Compatibility with the QCPU remote password function

This section explains the Q series C24 data communication for the QCPU remote password function.

Refer to Page 70, Section 3.1.1 for an overview of the Q series C24 check function for the QCPU remote password.

● The remote password function is a function that has been added to the QCPU as a means of preventing improper access

(such as destroying a program or data) from an external device. However, this function cannot completely prevent

improper access.

● The user should incorporate his/her own safeguards when it is necessary to protect the security of the programmable

controller system from improper access from an external device.

● The company cannot assume any responsibility for any problems that may arise from system troubles caused by

improper access.

An example of a safeguard on the programmable controller CPU with respect to improper access

One example is shown in Page 105, Section 3.3.6, in which the programmable controller CPU disconnects a line to the

external device when the number of times a "remote password mismatch" is detected exceeds the number set by the

user with regard to the Q series C24 remote password check explained in this section.

(1) Data communication during remote password setting

This section explains the use and setting of the QCPU remote password function and data communication

between the external device and the QCPU when a remote password has been set.

(a) Allowing/prohibiting access to the programmable controller from the external

device

1) Access allow processing (unlock processing)

• To access the specified QCPU, the external device performs the remote password unlock processing with

respect to the Q series C24

of the directly connected station (local station) after line connection for the

modem function.

• If the unlock processing has not been performed, the remote password check performed by the Q series

C24

that has received a communication request prohibits access to the specified station. ( Page 88,

Section 3.3.3 (2))

• All data communication before the unlock processing is performed will be processed as an error.

*1 The Q series C24 of the QCPU station for which a remote password is set will be indicated.

2) Access processing

• Normal completion of the remote password unlock processing allows the specified station to be accessed.

• Perform communication using MC protocol. (Perform on-line operation when GX Developer is connected.)

3) Access prohibition processing (lock processing)

• When the specified station access is completed, the process for disconnecting the line for the modem

function is performed in order to disable further access.

• When line disconnection is completed, the remote password lock processing is performed automatically.