Siemens S7-1200 System Manual page 260

Basic instructions
7.8 Program control operations
Parameter and type
R_PWD_ON OUT
HMI_PWD_ON OUT
Ret_Val OUT
Calling ENDIS_PW with REQ=1 disallows password types where the corresponding
password input parameter is FALSE. Each password type can be allowed or disallowed
independently. For example, if the fail-safe password is allowed and all other passwords
disallowed, then you can restrict CPU access to a small group of employees.
ENDIS_PW is executed synchronously in a program scan and the password output
parameters always show the current state of password allowance independent of the input
parameter REQ. All passwords that you set to allow must be changeable to
disallowed/allowed. Otherwise, an error is returned and all passwords are allowed that were
allowed before ENDIS_PW execution. This means that in a standard CPU (where the failsafe
password is not configured) F_PWD must always be set to 1, to result in a return value of 0.
In this case, F_PWD_ON is always 1.
Note
• ENDIS_PW execution can block the access of HMI devices, if the HMI password is
disallowed.
• Client sessions that were authorized prior to ENDIS_PW execution remain unchanged by
ENDIS_PW execution.
After a power-up, CPU access is restricted by passwords previously defined in the regular
CPU protection configuration. The ability to disallow a valid password must be re-established
with a new ENDIS_PW execution. However, if ENDIS_PW is immediately executed and
necessary passwords are disallowed, then TIA portal access can be locked out. You can use
a timer instruction to delay ENDIS_PW execution and allow time to enter passwords, before
the passwords become disallowed.
Note
Restoring a CPU that locks out TIA portal communication
Refer to the "Recovery from a lost password (Page 136)" topic for details about how to erase
the internal load memory of a PLC using a memory card.
An operating mode change to STOP caused by errors, STP execution or STEP 7 does not
abolish the protection. The protection is valid until the CPU is power cycled. See the
following table for details.
Action
After memory reset from
STEP 7
After powering on, or changing
a memory card
260
Data type Description
Bool Read only password status: Allowed (=1) or disallowed (=0)
Bool HMI password status: Allowed (=1) or disallowed (=0)
Word Function result
Operating mode
STOP
STOP
ENDIS_PW password control
Active: Disallowed passwords
remain disallowed.
Off: No passwords are
disallowed.
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG