An active low pulse is a digital signal that achieves its active function as it pulses from a higher voltage logic level to the lower voltage and then back the higher level again. With CMOS type logic on 5 volt supplies this would be a pulse that transitions from near +5V to GND and then back toward +5V. An example of an active low pulse would be the PSEN signal on the external code memory bus of the 8051.


Michael Karas