Table of Contents
Advertisement
Rules for Failsafe Operation of an S5-95F
18.13
Special Programming Features
To ensure the failsafety of systems which require approval, a number of STEP 5 operations have
been restricted or may not be used at all.
18.13.1 Disabling/Enabling Interrupts
Note that the STATUS function cannot be used on blocks which are invoked between an IA and an
RA operation in the quasi-safety mode.
Safety Note
Note that the interrupt response time may increase by the duration of the interrupt
disable. If possible, never disable interrupts for more than 5 ms. If they are disabled for a
longer period, the S5-95F responds as follows:
•
After 5 ms, the S5-95F reports error 13, i.e. "Error in user program, interrupts
disabled too long". There is no other response (the system remains at RUN).
•
After 10 ms, the S5-95F reports error 4, i.e. "Too many interrupts", and goes to
STOP to protect its failsafety.
If your process requires a system response after 5 ms, you must program it yourself.
Single out the error with the number 13 by evaluating the system event DB in OB37.
18.13.2 Restrictions for LIR, TIR, TNB and TBS Operations
The S5-95F monitors attempts to access address areas to which the user has no access.
Table 18-9. Impermissible Address Areas for LIR, TIR and TNB Operations
Operation
LIR
TIR
TNB
Warning
!
The TIR, TBS and TNB operations are memory-modifying operations which allow you to
access user memory and/or the system data area. Improper use of these operations may
lead to changes in the user program and to S5-95F malfunctions.
18-26
Access is forbidden to address areas
4F00
... 4FFF
H
H
5900
... 5C7F
H
H
6400
... 65FF
H
H
7000
... 73FF
H
H
8000
... FFFF
H
H
Access is allowed to the flag area and open data blocks only
For all source bytes: Same restrictions as LIR
For all destination bytes: Same restrictions
Restriction
as TIR
S5-95F
EWA 4NEB 812 6210-02
Advertisement
Table of Contents
