AN2690 Freescale Semiconductor / Motorola, AN2690 Datasheet - Page 21

• Manufacturer Part Number: AN2690
• Description: Low Frequency EEPROM Emulation on the MC68HLC908QY4
• Manufacturer: Freescale Semiconductor / Motorola

TimerISR Flow
Diagram
MOTOROLA
Low Frequency EEPROM Emulation on the MC68HLC908QY4
This routine is the interrupt service routine (ISR) for the timer overflow. The
SYSTEM_TICK_FLAG is set on every entry of the ISR to indicate a 10 ms
timeout. The ISR also sets the UPDATE_LED_TICK every second to time the
update rate for the LEDs. Finally, the interrupt is serviced by clearing the TOF
flag, before exiting the ISR.
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Figure 13. Timer Interrupt Service Routine
N
LedTimeOutCount = 0?
Dec LedTimeOutCount
SYSTEM_TICK_FLAG
UPDATE_LED_FLAG
LedTimeOutCounter
save H onto stack
Clear TOF Flag
Timer_isr
Reset
RTI
Set
Set
Y
Appendix A: Sample Application
AN2690
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