User guide

29
Chapter
29–1
Understanding the User Fault Routine – SLC
5/02 Processor Only
This chapter applies to the SLC 5/02 processor only. It covers the following
topics:
• recoverable and non–recoverable user faults
• application examples of user fault subroutines
The SLC 5/02 processor allows you to designate a subroutine file as a User
Fault Routine. This file will be executed when any recoverable or
non-recoverable user fault occurs. The file is not executed for non-user
faults.
The User Fault Routine gives you the option of preventing a processor
shutdown upon the occurrence of a specific user fault. You do this via the
designated subroutine by entering a ladder program which will prevent the
fault from occurring. You can handle a number of user faults in this way, as
the example on page 29–6 shows.
All application examples shown are in the HHT zoom display.
Status File Data Saved
Data in the following words is saved on entry to the designated subroutine
and re-written upon exiting the subroutine.
• S:0 Arithmetic flags
• S:13 and S:14 Math register
• S:24 Index register
Faults are classified as recoverable and non-recoverable user faults, and
non-user faults. A complete list appears in chapter 27, “Status File.”
Definitions:
Non-User Fault Non-Recoverable User Fault Recoverable User Fault
The user fault routine
does not execute.
The user fault routine executes for 1 pass.
(Hint: You may initiate a MSG instruction
to another node to identify the fault
condition of the processor.)
The user fault routine
may clear the fault by
clearing bit S:1/13.
Recoverable and non-recoverable user faults are listed on the following
pages. Refer to chapters 27 and 28 for additional information.
Overview of the User Fault
Routine
Recoverable and
Non–Recoverable User Faults