This tab allows you to enter functions to install an ISR and restore the old ISR. It assumes that the RTOS supports Virtual Interrupt Tables. As restoring an ISR is same OS call as installing one, the Restore ISR Function Name is forced to be same as the ISR Install Function Name.
The difference between both lies in the parameters they receive. The ISR Install function receives the ISR functions crated by Processor Expert when generating code, whereas the Restore ISR function should use values of the original ISR installed in the RTOS before executing the Init() function.
The Install ISR function executes in Init() and Restore executes at DeInit(). In most RTOSs, the DeInit() is never executed as RTOS do not support dynamic device driver load and unload.
In case of MQX, you need three parameters to install an ISR in the system: the IRQ number, the ISR function name, and its data I/O data structure.
In CDE, the values are:
- Installation - IRQ Vector Number, ISR function, and ISR Function Parameter. They will be replaced by the correct values at Processor Expert code generation.
- Restore - IRQ Vector Number, Original ISR Function, and Original ISR Input Parameter.
Note: The last two parameters depend on the RTOS to provide functions to retrieve the I/O data structure pointer and the ISR function pointer from the virtual interrupt table. If no functions are provided by the operating system, it is not possible to restore the old ISR. Therefore, it would be safe to use the same parameters as the install function.
In MQX, the ISR Install function is called _int_install_isr that provides functions to retrieve ISR function pointers and ISR input data structures. If an RTOS does not use Virtual Interrupt Tables, it might not provide installation and/or restore ISR functions so that all these fields can be left empty.