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System data RS 120
Password
Specifying the
password/activating protection
Deleting the
password/deactivating
protection
Maximum of five attempts to
delete
How to specify or delete the
password
CPU 948 Programming Guide
C79000-G8576-C848-04
Bit Assignment of the System Data Words
Software protection
System data RS 120 controls the system function "software
protection". With this function, you can prevent blocks being read,
overwritten or deleted by the PG (e.g. by unauthorized personnel) by
specifying a password.
The "software protection" function is linked to a password. The
system program is informed of this via RS 120.
By specifying a password in RS 120, the password protection is
automatically activated.
You can specify a new password after deleting the old one.
If you delete the password, password protection is automatically
deactivated.
When the password is deleted, the system program must be informed
via RS 120.
If you attempt to delete the password and specify the wrong password,
the attempt is rejected by the system program and a count started.
After a maximum of five unsuccessful attempts, the system program
will no longer accept password entries. The password can then only be
deleted after a COLD RESTART.
If the password is successfully deleted, the error counter is reset.
The password is specified/deleted (and the software protection
activated/deactivated) by writing a bit pattern in RS 120 (see
Assignment when writing) in one of the following ways:
• • by the STEP 5 program or
• • with a PG job "output address".
Note
When you first receive your CPU and following an overall reset,
the password is deleted and the software protection switched off.
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