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S5-95F
14.5
Measures for Securing the User Program Against Errors
Measures for Securing the User Program with the S5-95F
Before storing the user program (including DB1) on EPROM, it must be run on the S5-95F at least
once in Test mode . It is absolutely necessary that the S5-95F execute the user program because it
computes a checksum each time the RESTART routine is run and enters it into DB1.
The S5-95F uses the checksum computed in test mode in its failsafe RESTART routine to check the
user program. This allows the S5-95F to check for program integrity, which is a basic prerequisite
for any failsafe system.
Note
The user program checksum can be computed only in the S5-95F. Do not confuse the
checksum with the checksum for the test file generated with COM 95F.
Securing the User Program with the COM 95F Software Package
The COM 95F software provides a second means of securing the user program in the form of a
specially-developed conformance tool. The conformance tool uncovers dangerous systematic
faults/errors and hardware failures in the programmer (refer to the COM 95F Manual for details).
14.6
Storing the User Program on Memory Submodules
For operation in safety mode, you must store your user program on EPROMs. Each basic unit must
have a separate EPROM. The EPROMS have identical contents and are exactly the same.
The following table shows you how to store your user program on a memory submodule (EPROM).
Step
1
Test user program on S5-95F in test mode
2
Call STEP 5 block transfer package.
Read tested user program out of S5-95F and store it on diskette/hard disk
(see programmer manual).
3
Call STEP 5 EPROM programming package.
Copy user program from diskette/hard disk to EPROM
(see programmer manual).
4
Perform comparison to check for changes and corruptions using the acceptance
tool (see COM 95F manual).
EWA 4NEB 812 6210-02
Testing the User Program and Storing It on the Memory Submodule
Table 14-8. Storing a User Program on EPROM
Action
14-15
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