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© 2008 Microchip Technology Inc. DS01229A-page 1
AN1229
INTRODUCTION
This application note describes the Class B Safety
Software Library routines that detect the occurrence of
Faults in a single channel CPU. These routines have
been developed in accordance with the IEC 60730
standard to support the Class B certification process.
These routines can be directly integrated with the end
user’s application to test and verify the critical function-
alities of a controller without affecting the end user’s
application.
This application note also describes the Application
Programming Interface (API) functions that are
available in the Class B Safety Software Library.
The Class B safety software routines can be called
periodically at start-up or run time to test the following
components:
• CPU Registers
• CPU Program Counter
• Invariable Memory
• Variable Memory
•Clock
• Interrupt Handling and Execution
This application note also outlines various techniques,
which are not part of the Class B Safety Software
Library, to test components such as external communi-
cation, timing, I/O periphery, analog I/O and analog
multiplexer.
OVERVIEW OF THE IEC 60730
STANDARD
The IEC 60730 standard defines the test and diagnostic
methods that ensure the safe operation of the controlled
equipment used in household appliances. Annex H of
the IEC 60730 standard classifies the software into the
following categories (see Appendix B: “IEC 60730-1
Table H.11.12.7”):
•Class A
•Class B
•Class C
The Class B Safety Software Library implements the
important test and diagnostic methods that fall into the
Class B category. These methods use various
measures to detect and respond to the software-
related Faults and errors.
According to the IEC 60730 standard, the controls with
functions that fall into the Class B category should have
one of the following structures:
• Single Channel with Functional Test
In this structure, the Functional test is executed
prior to the application firmware execution.
• Single Channel with Periodic Self-Test
In this structure, the Periodic tests are embedded
within the firmware, and the self-test occurs
periodically while the firmware is in Execution
mode.
• Dual Channel without Comparison
In this structure, two independent methods execute
the specified operations.
Note: The term ‘IEC 60730 standard’ used in
this document refers to the “IEC 60730-1
ed.3.2” Copyright © 2007 IEC, Geneva,
Switzerland. www.iec.ch.
Author: Veena Kudva
Microchip Technology Inc.
Note: “The author thanks the International Elec-
trotechnical Commission (IEC) for permis-
sion to reproduce information from its
International Standard IEC 60730-1ed.3.2
(2007). All such extracts are copyright of
IEC, Geneva, Switzerland. All rights
reserved. Further information on the IEC is
available from www.iec.ch. IEC has no
responsibility for the placement and con-
text in which the extracts and contents are
reproduced by the author, nor is IEC in any
way responsible for the other content or
accuracy therein.”
Class B Safety Software Library for
PIC
®
MCUs and dsPIC
®
DSCs
