HCS08QG8 - Correct BDM connection

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HCS08QG8 - Correct BDM connection

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Contributor III

Hello,

 

I just want to confirm that on production board using the HCS08QG8 device that no external pullup resistors are required for the BMD header.  This application will use the P&E USB BDM Mulitlink tool to program the part.  The P&E tool has open drain outputs and the QG8 has pullup resistors for the RESET and BKGD\MS pins.  Knowing this, external pullup resistors are not required to program the part using the BDM?  

 

Thanks

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Contributor II

Hi FC,

 

I believe you are correct - external pullups are not required for the QG8 device. Note that the RESET pin on this device is not active on powerup. This means that CodeWarrior will prompt you to power cycle your board when begin debugging.

 

Best regards,

Edison

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Contributor IV

FC,

 

Edison is correct that both BKGD and RESET# have intenral pullups.  The QG8 datasheet does recommend an RC filter on the RESET# line in EMC sensitive lines.  Also if also you have a reset button in addition to the BDM conenctor on your board, you may want an RC filter there to filter out noise due to button presses so you don't get spurious resets due to key bounces.

 

See section 2 in the datasheet for details (it also has figure 2-4 which shows an example hookup of a BDM connector and reset button to a QG8)

 

Cheers,

 

Alan

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