Samsung manual S3F80JB Interrupt Structure

S3F80JB INTERRUPT STRUCTURE

The S3F80JB microcontroller supports twenty-four interrupt sources. Sixteen of the interrupt sources have a corresponding interrupt vector address; the remaining eight interrupt sources share by two vector address. Eight interrupt levels are recognized by the CPU in this device-specific interrupt structure, as shown in Figure 5-2.

When multiple interrupt levels are active, the interrupt priority register (IPR) determines the order in which contending interrupts are to be serviced. If multiple interrupts occur within the same interrupt level, the interrupt with the lowest vector address is usually processed first (The relative priorities of multiple interrupts within a single level are fixed in hardware).

When the CPU grants an interrupt request, interrupt processing starts: All other interrupts are disabled and the program counter value and status flags are pushed to stack. The starting address of the service routine is fetched from the appropriate vector address (plus the next 8-bit value to concatenate the full 16-bit address) and the service routine is executed.

5-3