many component failure with MC9s12xs128

[huguesangelis]

Hi all. I'm a teacher in a french university

Well it's been a couple year since I did a project board for my students using a MC9s12xs128.

I am experiencing a recuring hardware failure without having any explanation to give to my techs (witch repairs too often my students boards).

Here is a link to the schematics of the boards : MicroB12 (the MCU board) and XBoard (the connection board).

We are using both P&E USB BDM multilink (and I suspect them to be part of the problem) and (home made) TBDML.

Symptoms are : suddenly the RESET led on µB12 start blinking, 5V voltage power start fail to established (going hi to low and low to hi, at the same speed as reset led) and of course, the MCU overheat.

When I replace the µB12 board there is no longer any problem and everythings works properly. This problem happends most of the time with P&E programmer.

Does anyone experience such problem and does anyone got an idea of the way to solve it ?

Thanks to all

[takaoyamada]

Greetings,

I am Takao from P&E Micro. Maybe I can help.

A few questions I have:

1) Are you connecting all 4 important pins of the BDM using the 6-pin BDM ribbon cable? (RESET, BKGD, VDD, GND) The most popular issue we get from customers is that they did not connect VDD from the chip. As Daniel Lundin has detailed already, this is important to give the multilink a reference voltage for BKGD and RESET. Without it, the multilink has no idea if 3V is high or low or inbetween. Also, the multilink is partially powered by the USB cable and the VDD from the chip powers a few buffers on the multilink.

2) Are you using any custom ribbon cable, adapters, external watchdog, or other unique hardware between the multilink and your board?

3) Do you know if the multilink is in working condition? If the MCU overheated, it is possible the multilink is already damaged. Do you have other P&E hardware and if so you should see if those hardware work.

Takao Yamada

P&E Microcomputer Systems.

[Lundin]

Spontaneously, it sounds like the multilink is the culprit. Maybe you are powering the BDM multilink from the target, and the target can't handle that. Make sure it is getting its power from somewhere else. To verify that this is the cause of the problem, you could try to add a resistor (47k ohm or so) on the supply pin of the BDM connector. Supposedly the multilink should only use the supply pin to determine the voltage levels of the data and reset signals. Some older multilinks powered their whole pod from that supply, with the option to add an external power supply source.

I'd contact PE Micro support about the issue.