dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 140

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

When an interrupt occurs, the instruction at the interrupt starting address is fetched first.
Because the program flow is directed to a different starting address for each interrupt,
the interrupt structure of the DSP56K can be described as “vectored”. A vectored inter-
rupt structure has low execution overhead. If it is known beforehand that certain inter-
rupts will not be used, those interrupt vector locations can be used for program or data
storage.
7.3.3.1 Hardware Interrupt Sources
There are two types of hardware interrupts in the DSP56K: internal and external. The
internal interrupt sources include all of the on-chip peripheral devices. For further infor-
mation on a device’s internal interrupt sources, see the device’s individual User’s Man-
ual.
The external hardware interrupt sources are the RESET, NMI, IRQA, and IRQB pins on
the program interrupt controller in the Program Control Unit.
The level sensitive RESET interrupt is the highest priority interrupt with an IPL of 3. IRQA
and IRQB can be programmed to one of three priority levels: 0, 1, or 2 - all of which are
maskable. IRQA and IRQB have independent enable control and can be programmed to
be level sensitive or edge sensitive. Since level-sensitive interrupts will not be cleared
automatically when they are serviced, they must be cleared by other means to prevent
multiple interrupts. Edge-sensitive interrupts are latched as pending on the high-to-low
transition of the interrupt input and are automatically cleared when the interrupt is ser-
viced.
7 - 16
EXCEPTION PROCESSING STATE (INTERRUPT PROCESSING)
Starting Address
Interrupt
$0000
$0002
$0004
$0006
$0008
$000A
$001E
$003E
Freescale Semiconductor, Inc.
:
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For More Information On This Product,
Table 7-6 Interrupt Sources
PROCESSING STATES
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0 - 2
0 - 2
IPL
3
3
3
3
3
3
:
:
Hardware RESET
Stack Error
Trace
SWI
IRQA
IRQB
Vectors available for peripherals
NMI
Vectors available for peripherals
Illegal Instruction
Interrupt Source
MOTOROLA