Interrupt Detection and Processing
7-23
Interrupts
7.4.5
Actions Taken During RESET Interrupt Processing
A low signal on the RESET pin is the only requirement to process a reset. Once
RESET makes a high-to-low transition, the pipeline is flushed and CPU regis-
ters are returned to their reset values. GIE, NMIE, and the ISTB in the ISTP
are cleared. For the CPU state after reset, see section 7.3.3.1 on page 7-16.
During CPU cycles 15–21 of Figure 7–14, the following reset processing
actions occur:
-
Processing of subsequent nonreset interrupts is disabled because GIE
and NMIE are cleared.
-
A branch to the address held in ISTP (the pointer to the ISFP for INT0) is
forced into the E1 phase of the pipeline during cycle 16.
-
During cycle 16, IACK is asserted and the proper INUMx signals are
asserted to indicate a reset is being processed.
-
IF0 is cleared during cycle 17.
Note:
Code that starts running after reset must explicitly enable GIE, NMIE, and
IER to allow interrupts to be processed.