Can the Call instruction be used within an interrupt routine?
Answer Because of the limitations in size of the MCU Stack, programmers must be exceptionally careful if using a call instruction inside an interrupt routine. If the program is in an interrupt routine and the stack is full, then executing a call instruction will result in a stack-over situation preventing the program from returning properly from the interrupt routine. Therefore if it is necessary to execute call instruction from within interrupt routines it is imperative that the worst case condition regarding stack requirements are considered. Before entering interrupt routines it is essential to verify that enough stack levels are available.