29 September 1997 – Subject To Change
Clocks, Cache, and External Interface
4–59
Interrupts
4.13.1 Interrupt Signals During Initialization
The 21164PC interrupt signals work in tandem with the sys_reset_l signal to set the
values for clock ratios and clock delays. During initialization, the 21164PC reads
system clock configuration parameters from the interrupt pins. Section 4.2.2 and
Section 4.2.3 describe how the interrupt signals are used to set system clock values
when the system is initialized.
4.13.2 Interrupt Signals During Normal Operation
During normal operation, interrupt signals indicate interrupt requests from external
devices such as the real-time clock and I/O controllers.
4.13.3 Interrupt Priority Level
Table 4–11 shows which interrupts are enabled for a given interrupt priority level
(IPL). An interrupt is enabled if the current IPL is less than the target IPL of the
interrupt.
Table 4–11 Interrupt Priority Level Effect
(Sheet 1 of 2)
Interrupt Source
Target IPL
Source
Software Interrupt Request 1
1
Internal
Software Interrupt Request 2
2
Internal
Software Interrupt Request 3
3
Internal
Software Interrupt Request 4
4
Internal
Software Interrupt Request 5
5
Internal
Software Interrupt Request 6
6
Internal
Software Interrupt Request 7
7
Internal
Software Interrupt Request 8
8
Internal
Software Interrupt Request 9
9
Internal
Software Interrupt Request 10
10
Internal
Software Interrupt Request 11
11
Internal
Software Interrupt Request 12
12
Internal
Software Interrupt Request 13
13
Internal
Software Interrupt Request 14
14
Internal