Introduction
MOTOROLA
Interrupt Controller (ITCN)
8-3
Preliminary
8
8.1 Introduction
The Interrupt Controller (ITCN) is responsible for arbitrating all interrupt requests
according to the priority level of the each request. This includes all external interrupt
sources, such as IRQA, IRQB, and so on, peripheral generated interrupt requests and core
generated interrupt requests. After arbitration, the interrupt controller will compare the
priority of the current interrupt request with the current priority level of the core and if the
request has higher priority to generate a single enabled interrupt request signal to the core.
There are five levels of interrupt priority provided by the DSP56800E core, illustrated in
1. LP = the lowest level is generated by the SWILP instruction
2. Level 0 = maskable with the lowest priority of the three maskable interrupts
3. Level 1 = maskable
4. Level 2 = maskable
5. Level 3 = the highest priority is a non-maskable interrupt
Device interrupt priority levels are programmable via the Interrupt Priority Register (IPR).
The interrupt controller is also responsible for generating the vector address of the current
interrupt request. This is based on the Vector Address Base (VAB) register and the event
initiating the request. The interrupt controller predefines the Vector Table offsets for all
possible interrupt sources and will generate the Vector Address of the request by adding
the programmable VAB register to the Vector Table offset.
External interrupt sources such as IRQA and IRQB are programmable to either level
sensitive or edge triggered. Level sensitive interrupts remain active as long as the input
remains low and are cleared when the input level goes high. The edge sensitive interrupts
Table 8-1. Interrupt Priority Level
IPL
Description
Priority
Interrupt Sources
LP
Maskable
Lowest
SWILP instruction
0
Maskable
—
On-chip peripherals, IRQA and IRQB,
SWI #0 instruction
1
Maskable
—
On-chip peripherals, IRQA and IRQB,
SWI #1 instruction, EOnCE interrupts
2
Maskable
—
On-chip peripherals, IRQA and IRQB,
SWI #2 instruction, EOnCE interrupts
3
Non-maskable
Highest
Illegal instruction, HWS overflow,
SWI #3 instruction, EOnCE interrupts,
Misaligned data access