Ruth Hendrix

Vcc1, Vcc1 Question for 9S12E128

Discussion created by Ruth Hendrix Employee on Jan 26, 2006
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Posted: Tue Feb 22, 2005 4:08 pm
Hi there:

I am assembling a prototype using a MC9S12E128CFU device. By error, the Vdd1 and Vdd2 pins got connected to Vcc=3.3V
Right from the start, the P&E BDM box had a hard time recognizing the device (mostly indicating 'Bad device').I got to program the part once, and the code was running, but I wasn't able to reprogram any more.

Checking the circuit, I found the wrong connection and disconnected Vdd1 and Vdd2 from the 3.3V. Now the BDM box doesn't find the target ever and the code initially programed doesn't run at all. I suspect the MCU core is damaged from the 3.3V connection.

Has anybody had this experience before and would be able to confirm my theory?

Is there any thing to check before proceding with the MCU replacement?


Thanks.
Posted: Tue Feb 22, 2005 5:23 pm   
Hi There:

I got a reply from the Yahoo HCS12 forum. It suggested to check if the part got secured and unsecure it by using the program unsecure_12 provided free by P&E on their web site (www.pemicro.com).

I installed the program and I was able to unsecure the part. Now it programs again and runs code ok.

A question remains: how did it get secured on the first place?

Any suggestions?

Thanks
Posted: Wed Feb 23, 2005 11:43 am   
This can easily happen if the program download is interrupted and/or corrupted. Bear in mind that when you erase the flash, the micro is secured by default. You need to program location 0xFF0E after erasing the flash to make sure the micro will not get secured following the next reset.

If the location 0xFF0E got erased, but was not programmed to the unsecured state, the part will be secured. I am not sure which method you used to download the program into the micro, but if that method involved erasing the flash, programming the code and only then programming location 0xFF0E then you have a possible explanation...

Posted: Thu Feb 24, 2005 3:34 pm   

Hi:

Thank you for your answer. I am using the P&E USB BDM box to program the device. Probably during my attemps to program the device when it has out of spec voltages, the part got secured.

I'll pay attention to the 0xFF0E memory location.

Cheers,

Posted: Fri Feb 25, 2005 7:43 am   

Hi,

actually another point to watch out for is that this location receives the "unsecured" value from the ABS (or S19) file of your project. Normally this location is treated as part of the vector table:

Code:

void (*const _vectab[])(void) = { (void*)0xFFFF, /* 0xFF00 backdoor key */ (void*)0xFFFF, /* 0xFF02 */ (void*)0xFFFF, /* 0xFF04 */ (void*)0xFFFF, /* 0xFF06 */ (void*)0xFFFF, /* 0xFF08 */ (void*)0xFFFF, /* 0xFF0A */ (void*)0xFFFF, /* 0xFF0C */ (void*)0xFFFE, /* 0xFF0E security */ dummit, /* 0xFF10 Spurious Interrupt */ 


...

 

Regards,

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