There are two interrupt registers, interrupt enable (mask) and interrupt request (status). Each register has both a read and a write address. The names of the interrupt addresses are: INTENA Interrupt0 enable (mask) - write only. Sets or clears specific bits of INTENA. INTENAR Interrupt enable (mask) read - read only. Reads contents of INTENA. INTREQ Interrupt request (status) - write only. Used by the processor to force a certain kind of interrupt to be processed (software interrupt). Also used to clear interrupt request flags once the interrupt process is completed. INTREQR Interrupt request (status) read - read only. Contains the bits that define which items are requesting interrupt service. The bit positions in the interrupt request register correspond directly to those same positions in the interrupt enable register. The only difference between the read-only and the write-only addresses shown above is that bit 15 has no meaning in the read-only addresses.