AVR-Chat

David -

Are any of the alternate functions for that pin being activated (pin  
interrupts, etc)? It sounds like it might be going off on an interrupt  
with no vector, or something.

Jim Wagner

On Mar 29, 2009, at 10:57 AM, David VanHorn wrote:

> Is there something unusual I should know with this device?
>
> I'm watching it step through a simple routine to light some LEDs, and
> after stepping through a single CBI instruction it's telling me that
> half of SRAM has been changed..
>
> There are four alarm timers, and if any of them is > 0, I want to
> light the appropriate LED, if the timer is Zero, then turn the LED
> off.
>
> Sane at this point:
>
> 1638: if (A_Alarm_Timer > 0) {
> +000004C1: 9180022E LDS R24,0x022E Load direct from data space
> +000004C3: 2388 TST R24 Test for Zero or Minus
> +000004C4: F019 BREQ PC+0x04 Branch if equal
> 1639: LED_DDR	 |= (1 << LED_1);	 // Output
> +000004C5: 9A24 SBI 0x04,4 Set bit in I/O register
> 1640: LED_Port	|= (1 << LED_1);	 // High	
> +000004C6: 9A2C SBI 0x05,4 Set bit in I/O register
> +000004C7: C001 RJMP PC+0x0002 Relative jump
> 1642: LED_Port &= ~(1 << LED_1);	 // Low
> +000004C8: 982C CBI 0x05,4 Clear bit in I/O register
> 1646: if (A_Warn_Timer > 0) {
> +000004C9: 91800230 LDS R24,0x0230 Load direct from data space
> +000004CB: 2388 TST R24 Test for Zero or Minus
> +000004CC: F019 BREQ PC+0x04 Branch if equal
> 1647: LED_DDR	 |= (1 << LED_2);	 // Output
> +000004CD: 9A25 SBI 0x04,5 Set bit in I/O register
> 1648: LED_Port	|= (1 << LED_2);	 // High	
> +000004CE: 9A2D SBI 0x05,5 Set bit in I/O register
> +000004CF: C001 RJMP PC+0x0002 Relative jump
>
> Sane to this point
>
> 1650: LED_Port &= ~(1 << LED_2);	 // Low
> +000004D0: 982D CBI 0x05,5 Clear bit in I/O register
>
> BOOM. Total corruption of SRAM, stack pointer blown, all hope abandon
> ye who enter here..
>
> The device itself, without the ICE, is crashing when I run this
> routine, so I'm thinking it muse be some wild config problem.
> I'm running 20 MHz external crystal, and that's confirmed by the 1mS
> interrupt and serial baud rate being correct.
>
> Fuses:
> BODLEVEL is set at 4.3V, (VCC is solid at 5.05V)
> JTAGEN is checked
> SPIEN is checked
> EESAVE is checked
> BOOTSZ is 512 words (I'm not using it)
> SUT_CKSEL is Ext Xtal osc, 8.0 - 16k clock + 65mS
>
> -- 
> There is no computer problem which cannot be solved by proper
> application of a sufficiently large hammer.
>
> 



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