John Murphy

M9S08QG8 Serial Monitor Problem

Discussion created by John Murphy on May 25, 2006
Latest reply on May 26, 2006 by David Payne


I am trying to design an MC9S08QG8 circuit board that uses the HCS08 serial monitor for programming and debugging.  My circuit looks like the one pictured on page 25 of the MC9S08QG8 Data Sheet. When I try to download a program to the board, however, CodeWarrior (Development Studio version 5.7.0) cannot establish a connection.

I also have the M68DEMO908GB60 demonstration board.  With this board, I am able to successfully download and run programs using CodeWarrior in serial mode.  With the M68DEMO908GB60 demonstration board, the crystal circuit begins to oscillate as soon as CodeWarrior tries to establish communications.  My crystal circuit does not oscillate, although it is identical to the one on the M68DEMO908GB60 demonstration board (the component values are identical – I do not know the exact part numbers for the demonstration board – but the oscillator is designed as recommended in the specification).

Out of desperation, I have redesigned the board with nothing but the HCS08, the crystal oscillator circuitry, and the serial communications interface.  When CodeWarrior tries to establish communications, I can see activity on the serial port (pin 12), but no oscillation.  The frequency is varying in an attempt to find a suitable baud rate.

Any suggestions or observations would be greatly appreciated.  I am an experienced HC08 designer, but this is my first HCS08 project.

Thank you.