DSPIC30F datasheet(41/220 Pages) MICROCHIP

41 / 220 page

 2004 Microchip Technology Inc.

Preliminary

DS70116C-page 39

dsPIC30F5011/5013

5.0

INTERRUPTS

The dsPIC30F Sensor and General Purpose Family

has up to 41 interrupt sources and 4 processor excep-

tions (traps) which must be arbitrated based on a

priority scheme.

The CPU is responsible for reading the Interrupt Vector

Table (IVT) and transferring the address contained in

the interrupt vector to the program counter. The inter-

rupt vector is transferred from the program data bus

into the program counter via a 24-bit wide multiplexer

on the input of the program counter.

The Interrupt Vector Table (IVT) and Alternate Interrupt

Vector Table (AIVT) are placed near the beginning of

program memory (0x000004). The IVT and AIVT are

shown in Figure 5-1.

The

interrupt

controller

responsible

for

pre-

processing the interrupts and processor exceptions

prior to them being presented to the processor core.

The peripheral interrupts and traps are enabled, priori-

tized and controlled using centralized Special Function

Registers:

• IFS0<15:0>, IFS1<15:0>, IFS2<15:0>

All interrupt request flags are maintained in these

three registers. The flags are set by their respec-

tive peripherals or external signals, and they are

cleared via software.

• IEC0<15:0>, IEC1<15:0>, IEC2<15:0>

All interrupt enable control bits are maintained in

these three registers. These control bits are used

to individually enable interrupts from the

peripherals or external signals.

• IPC0<15:0>... IPC10<7:0>

The user assignable priority level associated with

each of these 41 interrupts is held centrally in

these twelve registers.

• IPL<3:0>

The current CPU priority level is explicitly stored

in the IPL bits. IPL<3> is present in the CORCON

STATUS register (SR) in the processor core.

• INTCON1<15:0>, INTCON2<15:0>

Global interrupt control functions are derived from

these two registers. INTCON1 contains the con-

trol and status flags for the processor exceptions.

The INTCON2 register controls the external

interrupt request signal behavior and the use of

the alternate vector table.

All interrupt sources can be user assigned to one of 7

priority levels, 1 through 7, via the IPCx registers. Each

interrupt source is associated with an interrupt vector,

as shown in Table 5-1. Levels 7 and 1 represent the

highest and lowest maskable priorities, respectively.

If the NSTDIS bit (INTCON1<15>) is set, nesting of

interrupts is prevented. Thus, if an interrupt is currently

being serviced, processing of a new interrupt is pre-

vented even if the new interrupt is of higher priority than

the one currently being serviced.

Certain interrupts have specialized control bits for fea-

tures like edge or level triggered interrupts, interrupt-

on-change, etc. Control of these features remains

within the peripheral module which generates the

interrupt.

The DISI instruction can be used to disable the

processing of interrupts of priorities 6 and lower for a

certain number of instructions, during which the DISI bit

(INTCON2<14>) remains set.

When an interrupt is serviced, the PC is loaded with the

address stored in the vector location in program mem-

ory that corresponds to the interrupt. There are 63 dif-

ferent vectors within the IVT (refer to Table 5-1). These

vectors are contained in locations 0x000004 through

0x0000FE of program memory (refer to Table 5-1).

These locations contain 24-bit addresses and in order

to preserve robustness, an address error trap will take

place should the PC attempt to fetch any of these

words during normal execution. This prevents execu-

tion of random data as a result of accidentally decre-

menting a PC into vector space, accidentally mapping

a data space address into vector space, or the PC roll-

ing over to 0x000000 after reaching the end of imple-

mented program memory space. Execution of a GOTO

instruction to this vector space will also generate an

address error trap.

Note:

Interrupt flag bits get set when an interrupt

condition occurs, regardless of the state of

its corresponding enable bit. User soft-

ware should ensure the appropriate inter-

rupt flag bits are clear prior to enabling an

interrupt.

Note:

Assigning a priority level of ‘0’ to an inter-

rupt source is equivalent to disabling that

interrupt.

Note:

The IPL bits become read only whenever

the NSTDIS bit has been set to ‘1’.

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