56F8355_07 Datasheet, PDF (73/164 Pages) Freescale Semiconductor, Inc – 16-bit Digital Signal Controllers

Functional Description
• Programmable priority levels for each IRQ
• Two programmable Fast Interrupts
• Notification to SIM module to restart clocks out of Wait and Stop modes
• Drives initial address on the address bus after reset
For further information, see Table 4-5, Interrupt Vector Table Contents.
5.3 Functional Description
The Interrupt Controller is a slave on the IPBus. It contains registers allowing each of the 82 interrupt
sources to be set to one of four priority levels, excluding certain interrupts of fixed priority. Next, all of
the interrupt requests of a given level are priority encoded to determine the lowest numerical value of the
active interrupt requests for that level. Within a given priority level, 0 is the highest priority, while number
81 is the lowest.
5.3.1 Normal Interrupt Handling
Once the ITCN has determined that an interrupt is to be serviced and which interrupt has the highest
priority, an interrupt vector address is generated. Normal interrupt handling concatenates the VBA and the
vector number to determine the vector address. In this way, an offset is generated into the vector table for
each interrupt.
5.3.2 Interrupt Nesting
Interrupt exceptions may be nested to allow an IRQ of higher priority than the current exception to be
serviced. The following tables define the nesting requirements for each priority level.
Table 5-1 Interrupt Mask Bit Definition
SR[9]¹
SR[8]¹
Permitted Exceptions
Masked Exceptions
0
0
Priorities 0, 1, 2, 3
None
0
1
Priorities 1, 2, 3
Priority 0
1
0
Priorities 2, 3
Priorities 0, 1
1
1
Priority 3
Priorities 0, 1, 2
1. Core status register bits indicating current interrupt mask within the core.
Table 5-2 Interrupt Priority Encoding
IPIC_LEVEL[1:0]¹
00
01
10
Current Interrupt
Priority Level
No Interrupt or SWILP
Priority 0
Priority 1
Required Nested
Exception Priority
Priorities 0, 1, 2, 3
Priorities 1, 2, 3
Priorities 2, 3
56F8355 Technical Data, Rev. 12
Freescale Semiconductor
73
Preliminary