Re: [Simulavr-devel] two things

[John Regehr]

What would you think of code like this in intvecs.h?  The idea is that
each interrupt vector is associated with two bits: a flag bit and an
enable bit.

typedef struct _IntBit IntBit;

struct _IntBit {
    int addr;
    int bit;
};

typedef struct _IntVect IntVect;

struct _IntVect {
    char *name;                 /* The name of the interrupt. */
    int   addr;                 /* Where to vector to when interrupt occurs. */
    uint32_t can_wake;          /* If the interrupt occurs while in sleep
                                   mode, can it wake the processor? Each bit
                                   represents a different sleep mode which the
                                   processor might be in. */
    IntBit enable;
    IntBit flag;
};

The semantics, as I understand things, are these:

There are two kinds of interrupts (I get this from ATmega128(L) docs page
14).

The first has a flag bit, which becomes set when the interrupt is
triggered (or it can be set programmatically -- who sets the bit is
irrelevant).  The interrupt fires any time the flag bit is set && the
enable bit is set && the global enable bit is set.

The second kind of interrupt does not necessarily have a flag bit and if
the condition disappears before the CPU has a chance to handle the
interrupt, then the interrupt is lost.

John


--
John Regehr, address@hidden
Assistant Professor, School of Computing, University of Utah