Georgios Detorakis

Problem with MC9S08DZ60 entering BDM

Discussion created by Georgios Detorakis on May 25, 2012
Latest reply on May 30, 2012 by Georgios Detorakis


I am having a problem programming MC9S08DZ60. What is causing the problem in entering the BDM I suppose is the Capacitance of the Line cause I use a fairly long cable in a noisy environment.

In Application Note AN2727, its is a different family but the approach is the same, it is refered that 

t = R * C, where C is the nominal capacitance of the Line (100pf) and t is the 1/5 of the Communication Pulse width and R is the Resistance of the Line.

It is not easy to change the Installation Cabling sa changing the other two parameters woulb be better.

The Resistance could be changed by putting a pull up resistor between the BKGD pin and the Voltage Supply.

What I wanted to know is how can I change the frequency of the BDM communication thus increasing the t.

There are some programmers that put an external clock to the processor but in my pcb I already have an external oscillator of 8Mhz.

It seems that the communication now is made with a frequency of 24MHz.

One more thing to consider is that the microprocessor will be programmed for the first time.

In case the cabling has to be changed, what implementation would you purpose. For ow shielded ribbon cable is used but I think coaxial cable would have less capacitance and less interfearence.

thank you.