Page 133 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

1 14 Chapter Eleven

Reset Goes Active Reset Goes Inactive

Figure 11-9. RS latch: reset input goes active then inactive

states, but that some previous input sequence placed the latch in its set condi-
tion; that is, q is I and -q is O. Now consider what occurs when the reset input
is placed in its active state and then returns to its inactive state (Figure 11-9).
As a reminder, if any input to a NOR is 1, its output will be forced to 0,
and it's only if both inputs to a NOR are 0 that the output will be 1. Thus, when
reset is placed in its active (logic I) state -1, the q output from the first
gate is forced to O m. This O on q is fed back into the second gate
and, as both inputs to this gate are now 0, the -q output is forced to 1 m.

The key point to note is that the I on -q is now fed back into the first gate
ED.
When the reset input returns to its inactive (logic O) state /TTh', the I
from the -q output continues feeding back into the first gate m, which
means that the q output continues to be forced to O m. Similarly, the O on
as
both
of
q continues feeding back into the second gate 19, this gate's
and
inputs are now at 0, the -q output continues to be forced to 1 In. The end