interrupt (for the DSP56800)

Controls the compilation of object code for interrupt service routines (ISR).

This pragma is compatible with the DSP56800, but it is not compatible with the DSP56800E. For the DSP56800E, see interrupt (for the DSP56800E).

#pragma interrupt [called|warn|saveall[warn]]

The compiler generates a special prologue and epilogue for functions so that they may be used to handle interrupts. The contents of the epilogue and prologue vary depending on the mode selected.

The compiler also emits an RTI or RTS for the return statement depending upon the mode selected. The SA, R, and CC bits of the OMR register are set to system default.

There are several ways to use this pragma as described below:

• pragma interrupt [warn]

  The compiler performs the following using the pragma interrupt [warn] argument:

  • Sets M01 to -1 if M01 is used by ISR
  • Sets OMR to system default (see OMR settings)
  • Saves/restores only registers used by ISR
  • Generates an RTI to return from interrupt.
  • If [warn] is present, then emits warnings if this ISR makes a function call that is not defined with #pragma interruptcalled

    Important considerations of usage:

  • This type of usage is required within the ISR function body as follows:

    void ISR(void)

    {

    #pragma interrupt

    ... code here

• pragma interrupt [called]

  The compiler performs the following using the pragma interrupt [called] argument:

  • Saves/restores only registers used by routine
  • Generates an RTS to return from function

    Important considerations of usage:

  • You must use this argument before the interrupt body is compiled
  • You can use this argument on the function Syntax or within the function body as described below.

    On the function Syntax:

    #pragma interrupt called

    void function_called_from_interrupt (void);

    Within the function body:

    void function_called_from_interrupt (void)

    {

    #pragma interrupt called

    asm (nop);

    }

  • You should use this pragma for all functions called from #pragma interrupt enabled ISRs. This is optional for #pragma interrupt saveall enabled ISRs, since for this case, the entire context is saved.
• pragma interrupt saveall [warn]

  The compiler performs the following using the pragma interrupt saveall [warn] argument:

  • Always sets M01 to -1
  • Sets OMR to system default (see OMR settings)
  • Saves/restores entire hardware stack via runtime call
  • Generates an RTI to return from interrupt
  • If [warn] is present, then emits a warning if the ISR makes a function call that is not defined with #pragma interrupt called

    Important considerations of usage:

  • This type of usage is required within the ISR function body as follows:

    void interrupt_function(void)

    {

    #pragma interrupt saveall

    ... code here

  • Use this pragma if the runtime library is called by the interrupt routine

In the following table, the advantages and disadvantages of the interrupt and interrupt saveall pragmas are listed.