HP 5004A, Руководство по эксплуатации и обслуживанию

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8-32. Complex Logic Devices
8-33. Logic elements can b e combined t o produce very complex devices that can perform
more difficult functions.
A
control block symbol can b e used b o simplify understanding of many
complex devices. Several examples of complex devices are given here.
Selector Control Block used to simplify AND portion of a quad AND-OR select
gate. When is high, presented at the inputswill through.
When is high, the data presented at the "2" inputs will be gated through.
Register control block used to illustrate a quad D-type latch. There i s a common
active-low reset (R), and a common edge-triggered control input Since
there i s only onedependency relationship, thecontrolling input i s not numbered
and the controlled functions (D) are subscripted with a C.
I
Shift Register Control Block used to show common inputs to a bidirectional
shift register. Notice that means shift the contents to the right or down
by units. And means shift the contents to the left or up by "m" units.
Note: If it may be omitted. Inputs "a" and "b" single pins that
have two functions. lnput "a" enables one of the inputs to the top D-type flip-
flop
and also shifts the register contentsdown one unit. Input "b" enables
one of the inputs to the bottom flip-flop and also shifts the register contents
up one unit. lnput "c" loads all four flip-flops in parallel lnput is a
common reset. The output delay indicator i s used because thesearemaster-slave
flip-flops.
Counter Control Block used to show common inputs to a Presettable Decade
Counter. Notice that means count up (increment the count) by
means count down by "m." Note: if
it
may be omitted. Since
the flip-flops are master-slave, the output delay indicator
is
used. The
and notation defines when the carry and borrow outputs are
generated. They also define
it,
as a decade counter; a binary counterwould have
indicatedwith Flip-flop weighting is indicated in parenthesis.
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