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A Structural Testing Strategy for PLC Programs Specified by Function Block Diagram  

Jee, Eun-Kyoung (한국과학기술원 전자전산학과)
Jeon, Seung-Jae (삼성전자 Visual Display 사업부)
Cha, Sung-Deok (고려대학교 정보통신대학 컴퓨터.통신공학부)
Publication Information
Journal of KIISE:Software and Applications / v.35, no.3, 2008 , pp. 149-161 More about this Journal
Abstract
As Programmable Logic Controllers(PLCs) are frequently used to implement real-time safety critical software, testing of PLC software is getting more important. We propose a structural testing technique on Function Block Diagram(FBD) which is one of the PLC programming languages. In order to test FBD networks, we define templates for function blocks including timer function blocks and propose an algorithm based on the templates to transform a unit FBD into a flowgraph. We generate test cases by applying existing testing techniques to the generated flowgraph. While the existing FBD testing technique do not consider infernal structure of FBD to generate test cases and can be applied only to FBD from which the specific intermediate model can be generated, this approach has advantages of systematic test case generation considering infernal structure of FBD and applicability to any FBD without regard to its intermediate format. Especially, the proposed method enables FBD networks including timer function blocks to be tested thoroughly. To demonstrate the effectiveness of the proposed method, we use trip logic of bistable processor of digital nuclear power plant protection systems which is being developed in Korea.
Keywords
Programmable Logic Controller; Function Block Diagram; Software Testing; Structural Testing;
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