RPM Interrupt speed limit

Projects General Guidance
19

Maybe I am missing something, but I am unsure why no one has suggested simply using cli() and sei() to block interrupts whilst reading a totally ordinary int or long value, then unblocking.

#include <avr/interrupt.h> 

volatile long rpmcount;

 void rpm_fun()
 {
   rpmcount++;
 }

void setup() 
{  
  attachInterrupt(2, rpm_fun, RISING);
}

void loop()
{
 long count;

 cli();
 count = rpmcount;
 sei();

 // what do I want to do with this count now?
}

cli and sei are documented here: http://www.nongnu.org/avr-libc/user-manual/interrupt_8h.html