Siemens CPU 948 - Page 360

When is the software
protection
activated/deactivated?
A password can be specified at any time. Once it has been specified,
software protection is, however, only active at certain times, as shown
below:
•• in the SOFT STOP mode:
once after calling OB 38
1)
,
cyclically before calling OB 39
1),
•• in the START-UP mode:
once after calling the start-up OBs (OB 20, OB 21 OB 22),
•• in the RUN mode:
cyclically before calling OB 1.
Assignment of the system
data when writing
To call the software protection function, write system data RS 120
with a bit pattern for the function as shown in the following table.
Address: E F078H
High byte
Bit no. Assignment
15 Action bit: 1 = execute function
14 Function bit: 1 = set password, 0 = delete PW
13
Bit nos. 8 to 13 of a 14-bit password
12
11
10
9
8
Low byte
7
Bit nos. 0 to 7 of a 14-bit password
6
5
4
3
2
1
0
1)
Processing a request does not depend on OB 38 or OB 39 being loaded. This means
that software protection can be activated in the STOP mode.
Table 8-17 Assignment of RS 120 (software protection) when writing
Bit Assignment of the System Data Words
CPU 948 Programming Guide
8 - 36 C79000-G8576-C848-04