Hello Oleg,

It took me a long time to figure out to use PNP's transistors on 8051 output pins rather than NPN's.

After much grief I just decided to put a 7407 IC's on output's just to avoid the grief you can get your self into.

It's nice to read a good description of the numbers as presented by your above post.

This design by experience sure has been nice not to have to worry about the details.

Thanks,

Charles Bannister