Both outputs would be 0 (not the complement of each other). Further, if
both S and R became inactive (went to 0) simultaneously, it is not clear
to which state the latch would go (since either Q = 0 or Q = 1 would
satisfy the logic equations). What happens would depend on such issues
as whether they go to 0 at exactly the same time or one input goes to 0
ahead of the other, in which case the last 1 will dominate. Otherwise,
such factors that are beyond the normal interest of the logic designer
(such as the stray capacitance or the gain of the individual transistors)
will determine the final state. To avoid this problem, we ensure that both
inputs are not active simultaneously.
More complex latches can also be built. We will look at a gated latch,
as shown in Figure 6.6. When the Gate signal is inactive ( 0), SG and RG
are both 0, and the latch remains unchanged. Only when Gate goes to 1, can
a 0 or 1 be stored in the latch, exactly as in the simpler latch of Figure 6.5.