Quote:
Originally Posted by MPaulHolmes
The 1N4148 diode pulls PWM low while !CLEAR is active
|
Actually this is not guaranteed. The ATmega8 output when low can be as high as 0.7V. The diode forward voltage will be 0.7V or more meaning you are only certain of pulling the PWM signal down to 1.4V which is around the threshold of the input low condition of the CMOS NAND gate input. If you really want to have a hardware circuit I would use an AND gate with PWM and !CLEAR as inputs. (or a NAND gate followed by a NAND Invertor). Or (shudder) a transistor circuit.
Having diodes in digital logic circuits is something to avoid....except zeners as voltage protection devices.