APC_INTR_MASK
csr &= ~(APC_PPAUSE | APC_PMIE | APC_INTR_MASK);
csr &= ~APC_INTR_MASK;
csr &= ~APC_INTR_MASK; /* do not clear interrupts accidentally */
csr &= ~(APC_CPAUSE | APC_CMIE | APC_INTR_MASK);
csr &= ~APC_INTR_MASK;
csr &= ~APC_INTR_MASK; /* do not clear interrupts accidentally */
if ((csr & APC_INTR_MASK) == 0) /* any interrupt pending? */