DSPIC30F3010_13 Datasheet, PDF (45/228 Pages) Microchip Technology – High-Performance,16-Bit Digital Signal Controllers

5.0 INTERRUPTS
Note:
This data sheet summarizes features of
this group of dsPIC30F devices and is not
intended to be a complete reference
source. For more information on the CPU,
peripherals, register descriptions and
general device functionality, refer to the
“dsPIC30F Family Reference Manual”
(DS70046). For more information on the
device instruction set and programming,
refer to the “16-bit MCU and DSC
Programmer’s Reference Manual”
(DS70157).
The dsPIC30F3010/3011 has 29 interrupt sources and
4 processor exceptions (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 con-
tained in the interrupt vector to the program counter.
The interrupt vector is transferred from the program
data bus into the program counter through 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 is responsible for pre-
processing the interrupts and processor exceptions,
prior to their being presented to the processor core.
The peripheral interrupts and traps are enabled,
prioritized and controlled using centralized Special
Function Registers (SFR):
• 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>... IPC11<7:0>
The user-assignable priority level associated with
each of these 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 register, whereas IPL<2:0> are
present in the STATUS Register (SR) in the
processor core.
dsPIC30F3010/3011
• INTCON1<15:0>, INTCON2<15:0>
Global interrupt control functions are derived from
these two registers. INTCON1 contains the
control 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.
Note:
Interrupt flag bits get set when an interrupt
condition occurs, regardless of the state of
its corresponding enable bit. User
software should ensure the appropriate
Interrupt flag bits are clear prior to
enabling an interrupt.
All interrupt sources can be user-assigned to one of
7 priority levels, 1 through 7, through the IPCx regis-
ters. Each interrupt source is associated with an inter-
rupt vector, as shown in Table 5-1. Levels 7 and 1
represent the highest and lowest maskable priorities,
respectively.
Note:
Assigning a priority level of 0 to an
interrupt source is equivalent to disabling
that interrupt.
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
prevented, even if the new interrupt is of higher priority
than the one currently being serviced.
Note: The IPL bits become read-only whenever
the NSTDIS bit has been set to ‘1’.
Certain interrupts have specialized control bits for
features like edge or level triggered interrupts, inter-
rupt-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
memory that corresponds to the interrupt. There are 63
different vectors within the IVT (refer to Figure 5-2).
These vectors are contained in locations 0x000004
through 0x0000FE of program memory (refer to
Figure 5-2). 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
execution of random data as a result of accidentally
decrementing a PC into vector space, accidentally
mapping a data space address into vector space or the
PC rolling over to 0x000000 after reaching the end of
implemented program memory space. Execution of a
GOTO instruction to this vector space will also generate
an address error trap.
© 2010 Microchip Technology Inc.
DS70141F-page 45