Z-World OP7100, User Manual

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OP7100 Memory, I/O Map, and Interrupt Vectors s 105
Nonmaskable Interrupts
The
/NMI
line normally connects to the power-failure output of the
ADM691 supervisor. A nonmaskable interrupt (NMI) occurs when
PFI
falls to 1.25 V ± 0.05 V. This advanced warning allows the program to
perform some emergency processing before an unwanted power-down
occurs.
The NMI is edge-sensitive and cannot be masked by software. When
activated, the NMI disables all other interrupts (except TRAP), and begins
execution from logical address 0x66.
The following example shows how to handle a power-failure interrupt.
#JUMP_VEC NMI_VEC myint
interrupt retn myint(){
body of interrupt routine
while(!IBIT(WDO,0)){}
// input voltage is still below the threshold
// that triggered the NMI
return; // if just a power glitch, return
}
Jump Vectors
These special interrupts occur in a different manner. Instead of loading the
address of the interrupt routine from the interrupt vector, these interrupts
cause a jump directly to the address of the vector, which contains a jump
instruction to the interrupt routine. The following example illustrates a
jump vector.
0x66nonmaskable power-failure interrupt
Since nonmaskable interrupts (NMI) can be used for Dynamic C communi-
cations, an interrupt vector for power failure is normally stored just in front
of the Dynamic C program. Use the command
#JUMP_VEC NMI_VEC name
to store the vector here.
The Dynamic C communication routines relay to the jump vector when the
NMI is caused by a power failure rather than by a serial interrupt.