Direct call to ISR by an Interrupting Source

Question

Explain about the direct call to ISR by an interrupting source.

Answer 1

Direct call to ISR by an Interrupting Source:

• To ISR directly, a hardware source calls and ISR only sends a message to the RTOS. At an interrupt the process running on the CPU is interrupted and the ISR consequent to which source starts executing.
• RTOS is only sent a message by the ISR into a mailbox or message queue. This is to inform the RTOS about that ISR has obtained control of the CPU.
• The ISR carries on execution of the codes required interrupt service. The routine conveys a message for the RTOS. That message is stored at the memory selected for RTOS messages.
• While TSR finishes the RTOS returns to reschedules the processes or the interrupted process. RTOS action depends upon the messages at the mailbox.