Overview of Interrupts
7-4
7.1.1.3
Maskable Interrupts (INT4–INT15)
The ’C62x/C67x CPUs have twelve interrupts that are maskable. These have
lower priority than the NMI and reset interrupts. These interrupts can be
associated with external devices, on-chip peripherals, software control, or not
be available.
Assuming that a maskable interrupt does not occur during the delay slots of
a branch (this includes conditional branches that do not complete execution
due to a false condition), the following conditions must be met to process a
maskable interrupt:
-
The global interrupt enable bit (GIE) bit in the control status register (CSR) is
set to1.
-
The NMIE bit in the interrupt enable register (IER) is set to1.
-
The corresponding interrupt enable (IE) bit in the IER is set to1.
-
The corresponding interrupt occurs, which sets the corresponding bit in
the IFR to 1 and there are no higher priority interrupt flag (IF) bits set in the
IFR.
7.1.1.4
Interrupt Acknowledgment (IACK and INUMx)
The IACK and INUMx signals alert hardware external to the ’C62x and C67x
that an interrupt has occurred and is being processed. The IACK signal indi-
cates that the CPU has begun processing an interrupt. The INUMx signals
(INUM3–INUM0) indicate the number of the interrupt (bit position in the IFR)
that is being processed.
For example:
INUM3 = 0 (MSB)
INUM2 = 1
INUM1 = 1
INUM0 = 1 (LSB)
Together, these signals provide the 4-bit value 0111, indicating INT7 is being
processed.