topic Clarification on BKGD connection in 8-bit Microcontrollers

Clarification on BKGD connection

admin — Thu, 19 Nov 2009 12:11:02 GMT

Hi guys,

I read on the forum some where that the Vdd pin on the BKGD connector of the USB-ML-12E is a read pin, so when connecting to a target circuit that uses external power supply the Vdd pin on the BKGD connector is connected to the external power supply also.

Is this correct???

Re: Clarification on BKGD connection

Lundin — Thu, 19 Nov 2009 15:51:53 GMT

Yes the "V" pin of the connector is a voltage reference, so that you can use the BDM on both 3V and 5V targets.

Re: Clarification on BKGD connection

admin — Thu, 19 Nov 2009 21:12:19 GMT

Is there a Freescale document that covers this? I can not seem to find anything that talks about this.....

Re: Clarification on BKGD connection

Lundin — Fri, 20 Nov 2009 00:00:20 GMT

Various app notes like AN3335 for HCS08 or AN2104 for HCS12. Neither provides a definition to what "Vdd" is, however. The implementation of this seems to be pod-specific. Older BDM pods from PE could be supplied by the target from this pin, for example.

Re: Clarification on BKGD connection

EdT — Fri, 20 Nov 2009 00:53:02 GMT

Hi Learner,

The VDD pin on the the USB-ML-12E is indeed an INPUT to the multilink. The USB-ML-12E uses this to determine the logic voltage level of the target processor, which is the logic high voltage required for BKGD and RESET. The USB-ML-12E draws about 1mA of current on this pin.

Best regards,

Edison

Re: Clarification on BKGD connection

admin — Fri, 20 Nov 2009 06:12:53 GMT

Thank you so much guys for clearing this up.

1 more question, how did you guys find out about this???

I can't say I have read all the information available in relation to the HCS08 and the background debug pod but I certainly have yet to come accross information that clarifies this. Sigh......

I have been using the USB-ML-12E for some time now and all this time I have been programming my target board with the Vdd pin open, the target board is using external power supply. Recently the USB-ML-12E stopped working and I have requested technical support from both PE and Freescale, both times the technical support requested for my circuit wiring diagram.

After showing them the schematic and described how the pod is connected to my target board, NON of them picked up on this after exchanging many emails.

I SIMPLY CAN NOT BELIEVE IT!!!

I have placed a service request asking this exact question, it has been 4 days now and the Status is still Unassigned at this very moment.

Now it seems I have a USB-ML-12E that's not working and there isn't any documents with any clarification about this......

Sigh.......

Message Edited by Learner on 2009-11-19 10:15 PM