DSPIC33FJ12MC201TESS datasheet(71/304 Pages) MICROCHIP

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DS70265E-page 71

dsPIC33FJ12MC201/202

7.0

INTERRUPT CONTROLLER

The dsPIC33FJ12MC201/202 interrupt controller

reduces the numerous peripheral interrupt request

signals to a single interrupt request signal to the

dsPIC33FJ12MC201/202 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 (IVT) 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. Lower addresses generally have a higher

natural priority. For example, the interrupt associated

with vector 0 will take priority over interrupts at any

other vector address.

dsPIC33FJ12MC201/202 devices implement up to 26

unique interrupts and 4 nonmaskable traps. These are

summarized in Table 7-1 and Table 7-2.

7.1.1

ALTERNATE INTERRUPT 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 way to

switch between an application and a support

environment without requiring the interrupt vectors to

be reprogrammed. This feature also enables switching

between applications to facilitate 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 dsPIC33FJ12MC201/202 device clears its regis-

ters in response to a Reset, forcing the PC to zero. The

digital signal controller then begins program execution

at location 0x000000. A GOTO instruction at the Reset

address can redirect program execution to the

appropriate start-up routine.

Note 1:

This data sheet summarizes the features

of the dsPIC33FJ12MC201/202 family of

devices. It is not intended to be a

comprehensive reference source. To

complement the information in this data

sheet, refer to Section 6. “Interrupts”

(DS70184) of the “dsPIC33F/PIC24H

Family Reference Manual”

, which is

available on the Microchip website

(www.microchip.com).

Some registers and associated bits

described in this section may not be

available on all devices. Refer to

Section 4.0 “Memory Organization”

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.

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