topic Re: Production test equipment in 8-bit Microcontrollers

Production test equipment

Br — Wed, 06 Dec 2006 23:25:41 GMT

Hi,

I´m developing a production test equipment based on needles. In the way that I´m thinking, I will need to put 2 microcontrollers GT32 working in parallel (each pin connected with the other physically). The problem is that each microcontroller will execute differents programs. What problems can I find trying to do it?

Thanks

Emerson

Re: Production test equipment

Alban — Wed, 06 Dec 2006 23:40:12 GMT

Hello,

A few examples of problems:

- Short circuits on outputs with conflicting level --> MCU burnt

- Conflict in PLL CGMXFC level --> Wrong clock speed

- Conflict between ADC levels --> wrong ADC measures

- Input impedance divided --> draw more current

- Conflict in comms lines --> No message sent or received.

There are more problems...

Cheers,

Alban.

Re: Production test equipment

bigmac — Thu, 07 Dec 2006 02:42:59 GMT

Hello Emerson,

I am not entirely sure what you are trying to achieve. Are you attempting to test a MCU device or board, using another similar MCU containing test firmware, to automatically sequence inputs and sense the ouputs of the device under test?

If so, not all pins may be paralleled, as Alban has already indicated.

Some of the peripherals would need to be tested using entirely seperate sources of test excitation - the ATD inputs would fall in this category. Testing the SCI functionality would require that TXD on one device be connected to RXD of the other device, in each direction. It would also be a wise precaution to include series resistors to limit current in case there is I/O conflict.

Regards,

Mac

Re: Production test equipment

Br — Thu, 07 Dec 2006 23:45:44 GMT

Hi,

Consideranting only the pins directions. What kind of conflicts can happen connecting pins with differents or equal directions.

Regards,

Emerson

Re: Production test equipment

peg — Fri, 08 Dec 2006 05:04:18 GMT

Hi Emerson,

The biggest problem is if you tie two outputs together and one wants to be high and the other low. Things get hot and then stop working.

Regards

Peg