Allen-Bradley 1756-L6 Series, Reference Manual, Page: 80 / 134

80 Rockwell Automation Publication 1756-RM001I-EN-P - May 2012
Chapter 7 Requirements for Application Development
Basics of Application
Program Development and
Testing The application program is intended to be developed by the system integrator
and/or user. The developer must consider general procedures for programming
ControlLogix SIL 2 applications listed below (this does not require independent
third party review).
• Specification of the SIL 2 safety control function, including the following:
– Specifications
– Flow and timing charts
– Engineering diagrams
– Sequence charts
– Program description
– Program review process
• Writing the application program
• Checking by independent reviewer
• Verification and validation
All application logic must be independently reviewed and tested. To facilitate
reviews and reduce unintended responses, developers should limit the set of
instructions to basic Boolean/ladder logic (such as examine On/Off, Timers,
Counters, and so on) whenever possible. This set should include instructions that
can be used to accommodate analog variables, such as:
• limit tests.
• comparisons.
• math instructions.
For more information, see Proof Tests on page 20 .
Functional Specification
Guidelines You must create a specification for your control function. Use this specification to
verify that program logic correctly and fully addresses your application’s
functional and safety control requirements. The specification may be presented
in a variety of formats, depending on your application.
The specification must include a detailed description that includes the following
(if applicable):
• Sequence of operations
• Flow and timing diagrams
• Sequence charts
• Program description
• Program print out
• Written descriptions of the steps with step conditions and actuators to be
controlled, including the following:
– Input definitions
– Output definitions
– I/O wiring diagrams and references
– Theory of operation