DSPIC33FJ12MC02ESS datasheet(93/284 Pages) MICROCHIP

93 / 284 page

Preliminary

DS70265B-page 91

dsPIC33FJ12MC201/202

6.4

Interrupt Setup Procedures

6.4.1

INITIALIZATION

To configure an interrupt source at initialization:

Set the NSTDIS bit (INTCON1<15>) if nested

interrupts are not desired.

Select the user-assigned priority level for the

interrupt source by writing the control bits in the

appropriate IPCx register. The priority level will

depend on the specific application and type of

interrupt source. If multiple priority levels are not

desired, the IPCx register control bits for all

enabled interrupt sources can be programmed

to the same non-zero value.

Clear the interrupt flag status bit associated with

the peripheral in the associated IFSx register.

Enable the interrupt source by setting the inter-

rupt enable control bit associated with the

source in the appropriate IECx register.

6.4.2

INTERRUPT SERVICE ROUTINE

The method used to declare an ISR and initialize the

IVT with the correct vector address depends on the

programming language (C or assembler) and the

language development tool suite used to develop the

application.

In general, the user application must clear the interrupt

flag in the appropriate IFSx register for the source of

interrupt that the ISR handles. Otherwise, program will

re-enter the ISR immediately after exiting the routine. If

the ISR is coded in assembly language, it must be

terminated using a RETFIE instruction to unstack the

saved PC value, SRL value and old CPU priority level.

6.4.3

TRAP SERVICE ROUTINE

A Trap Service Routine (TSR) is coded like an ISR,

except that the appropriate trap status flag in the

INTCON1 register must be cleared to avoid re-entry

into the TSR.

6.4.4

INTERRUPT DISABLE

All user interrupts can be disabled using this

procedure:

Push the current SR value onto the software

stack using the PUSH instruction.

Force the CPU to priority level 7 by inclusive

ORing the value OEh with SRL.

To enable user interrupts, the POP instruction can be

used to restore the previous SR value.

The DISI instruction provides a convenient way to

disable interrupts of priority levels 1-6 for a fixed period

of time. Level 7 interrupt sources are not disabled by

the DISI instruction.

Note:

At a device Reset, the IPCx registers are

initialized such that all user interrupt

sources are assigned to priority level 4.

Note:

Only user interrupts with a priority level of

7 or lower can be disabled. Trap sources

(level 8-level 15) cannot be disabled.

DSPIC33FJ12MC02ESS Datasheet(PDF) 93 Page - Microchip Technology

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