The Safety Critical Systems Handbook, 4th Edition

Appendix 3

BETAPLUS CCF Model, Scoring Criteria

Checklist for Equipment Containing Programmable Electronics

A scoring methodology converts this checklist into an estimate of Beta. This is available as the BETAPLUS software package.

(1). Separation/segregation

Are all signal cables separated at all positions?

Are the programmable channels on separate printed circuit boards?

OR are the programmable channels in separate racks

OR in separate rooms or buildings?

(2). Diversity

Do the channels employ diverse technologies?

1 electronic + 1 mechanical/pneumatic

OR 1 electronic or CPU + 1 relay based

OR 1 CPU + 1 electronic hardwired?

Were the diverse channels developed from separate requirements from separate people with no communication between them?

Were the two ...