Interrupt Sources

1
Interrupt Sources

• IRQ is a maskable, general purpose external
  interrupt request.
• XIRQ is a non-maskable interrupt (after program
  enables it)
• Four other signals (pins) that may be used as
  interrupt inputs Pulse Accumulator Input Edge,
  Timer Input Capture 1, 2 and 3.
• There are ten internal interrupt sources Output
  Compare 1, 2, 3, 4 and 5, SCI, SPI, Pulse
  Accumulator Overflow, Timer Overflow, Real Time
  Interrupt are internal sources of Interrupts
• There are four other special interrupts Illegal
  Opcode, COP Failure, COP Clock Monitor Fail and
  SWI are special interrupts.

2
Configuring Interrupts

• Each source may have a global mask
• Each source may have a local (or individual)
  mask/enable
• Each source has a flag to indicate which
  interrupt is active
• General routine
• Install interrupt service routine
• Configure source (peripheral)
• Enable locally
• Enable globally (CLI)

3
Interrupt Sources
4
More Sources
5
Interrupt Vectors
6
ISR

• Do what you need to do
• Clear the Interrupt Flag
• The interrupt flag indicates which interrupt
  source caused the interrupt
• You must clear that flag or the ISR will
  continually execute
• You typically clear the respective flag by
  writing a 1 to that flags location
• Ex
• // real time interrupt flag RTIF (bit 6) in TFLG2
  indicates a RTI
• ldaa 0b01000000
• staa TFLG2 clears RTIF flag
• Issue RTI
• DO NOT issue CLI within ISR unless you know
  exactly what you are doing (nesting ISRs)