dsPIC30F Family Reference Manual
DS70053C-page 6-2 © 2004 Microchip Technology Inc.
6.1 Introduction
The dsPIC30F interrupt controller module reduces the numerous peripheral interrupt request
signals to a single interrupt request signal to the dsPIC30F CPU and has the following features:
• Up to 8 processor exceptions and software traps
• 7 user selectable priority levels
• Interrupt Vector Table (IVT) with up to 62 vectors
• A unique vector for each interrupt or exception source
• Fixed priority within a specified user priority level
• Alternate Interrupt Vector Table (AIVT) for debug support
• Fixed interrupt entry and return latencies
6.1.1 Interrupt Vector Table
The Interrupt Vector Table (IVT) is shown in Figure 6-1. The IVT resides in program memory,
starting at location 0x000004. The IVT contains 62 vectors consisting of 8 non-maskable trap
vectors plus up to 54 sources of interrupt. In general, each interrupt source has its own vector.
Each interrupt vector contains a 24-bit wide address. The value programmed into each interrupt
vector location is the starting address of the associated Interrupt Service Routine (ISR).
6.1.2 Alternate Vector Table
The Alternate Interrupt Vector Table (AIVT) is located after the IVT as shown in Figure 6-1.
Access to the AIVT is provided by the ALTIVT control bit (INTCON2<15>). If the ALTIVT bit is
set, all interrupt and exception processes will use the alternate vectors instead of the default
vectors. The alternate vectors are organized in the same manner as the default vectors.
The AIVT supports emulation and debugging efforts by providing a means to switch between
an application and a support environment without requiring the interrupt vectors to be
reprogrammed. This feature also enables switching between applications for evaluation of
different software algorithms at run-time. If the AIVT is not needed, the AIVT should be
programmed with the same addresses used in the IVT.
6.1.3 Reset Sequence
A device Reset is not a true exception because the interrupt controller is not involved in the Reset
process. The dsPIC30F device clears its registers in response to a Reset which forces the PC to
zero. The processor then begins program execution at location 0x000000. The user programs
a GOTO instruction at the Reset address which redirects program execution to the appropriate
start-up routine.
Note: Any unimplemented or unused vector locations in the IVT and AIVT should be
programmed with the address of a default interrupt handler routine that contains a
RESET instruction.
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