Application Test Units

Application Test Units (TU) are used by the Diagnostic Applications to test a device. Typically, due to either their large size or their functional composition, TUs are more appropriately written as applications as opposed to being included within device drivers.

This chapter defines requirements for Application Test Unit code and provides guidance for TU Developers who need to develop code for multiple target environments. The TU code should be developed in ANSI C language and according to generally accepted good programming practices, including, but not limited to:

• Modularity
• Readability
• Self Documenting
• Maintainability
• Re-entrant Capability

The use of assembler-level code is strongly discouraged, but may be necessary in certain cases where performance is critical to the effectiveness of the test function. Such code would not be considered portable and would have to be rewritten for the target platform.

The following topics are discussed in detail:

• Test Unit Definition
• Hardware Functional Coverage
• Test Unit Numbering
• Test Unit Code Device Open and Close
• Portability
• In-Service versus Out-of-Service Test Units
• Recommended General Structure of Test Unit Code
• Designing for Multitasking Environments
• Persistent Data and the TU_INFO_HANDLE
• Test Unit Call Interface
• Definition of TU_TYPE Input Structure
• Definition of TU_RETURN_TYPE Output Structure
• Return Codes
• Interrupt Handler Call Interface
• Interrupt Handling in Test Units
• Using the Interrupt Flag Bit Mask
• Programming Interfaces for TUs and Interrupt Handlers
• Configuration Services Device Attributes
• Message Handling
• Signal Handling
• Definition of EXECTU()