Datasheet

 2009-2012 Microchip Technology Inc. DS70593D-page 89
dsPIC33FJXXXGPX06A/X08A/X10A
7.0 INTERRUPT CONTROLLER
The dsPIC33FJXXXGPX06A/X08A/X10A interrupt
controller reduces the numerous peripheral interrupt
request signals to a single interrupt request signal to
the dsPIC33FJXXXGPX06A/X08A/X10A CPU. It has
the following features:
• Up to eight processor exceptions and software
traps
• Seven user-selectable priority levels
• Interrupt Vector Table (IVT) with up to 118 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
7.1 Interrupt Vector Table
The Interrupt Vector Table is shown in Figure 7-1. The
IVT resides in program memory, starting at location
000004h. The IVT contains 126 vectors consisting of
eight non-maskable trap vectors plus up to 118 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).
Interrupt vectors are prioritized in terms of their natural
priority; this priority is linked to their position in the
vector table. All other things being equal, lower
addresses have a higher natural priority. For example,
the interrupt associated with vector 0 will take priority
over interrupts at any other vector address.
dsPIC33FJXXXGPX06A/X08A/X10A devices imple-
ment up to 67 unique interrupts and five non-maskable
traps. These are summarized in Ta ble 7- 1 and
Table 7-2.
7.1.1 ALTERNATE VECTOR TABLE
The Alternate Interrupt Vector Table (AIVT) is located
after the IVT, as shown in Figure 7-1. Access to the
AIVT is provided by the ALTIVT control bit
(INTCON2<15>). If the ALTIVT bit is set, all interrupt
and exception processes 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 debugging 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.
7.2 Reset Sequence
A device Reset is not a true exception because the
interrupt controller is not involved in the Reset process.
The dsPIC33FJXXXGPX06A/X08A/X10A device
clears its registers in response to a Reset, which forces
the PC to zero. The digital signal controller 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 1: This data sheet summarizes the features
of the dsPIC33FJXXXGPX06A/X08A/
X10A family of devices. However, it is not
intended to be a comprehensive
reference source. To complement the
information in this data sheet, refer to
Section 6. “Interrupts” (DS70184) in
the “dsPIC33F/PIC24H Family
Reference Manual”, which is available
from the Microchip web site
(www.microchip.com).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
Section 4.0 “Memory Organization” in
this data sheet for device-specific register
and bit information.
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.