ATV2500B
3
Description
The ATV2500Bs are the highest density PLDs available in
a 40- or 44-pin package. With their fully connected l ogic
array and flexible macrocell structure, high gate utilization
is easily obtainable.
The ATV2500Bs are organized around a
single universal
and-or array
. All pin and feedback terms are always available to every macro ce ll. Eac h o f the 38 logic pins are array
inputs, as are the outputs of each flip-flop.
In the ATV2500Bs, four product terms are input to each
sum term. Furthermore, each macrocell's three sum terms
can be combined to provide up to 12 product terms per
sum term with
no performance penalty
. Each flip-flop is
individually se lecta ble to b e either D- or T -type, pr ovidin g
further logic compaction. Also, 24 of the flip-flops may be
bypassed to provide internal combinatorial feedback to the
logic array.
Product terms provide individual clocks and asynchronous
resets for each flip-flop. The flip-flops may also be individually configured to have direct input pin clocking. Each output has its own enable produc t term. Eight synchronous
preset product terms serve local groups of either four or
eight flip-flops. Register preload functions are provided to
simplify testing. All registers automatic ally reset upon
power up.
Several low power device options allow selection of the
optimum solution for many power -sensitive applic ations.
Each of the options significantly reduces total sy stem
power and enhances system reliability.
Functional Logic Diagram Description
The ATV2500B functional logic diagram describes the
interconnections betwee n the input, feedback p ins and
logic cells. All interc onnec tions are r outed th rough the si ngle global bus.
The ATV2500Bs are straightforward and uniform PLDs.
The 24 macrocells are numbered 0 through 23. Each macrocell contains 17 AND gates. All AND gates have 172
inputs. The five lower product terms provide AR1, CK1,
CK2, AR2, and OE. T hese are: one asy nchronous reset
and clock per flip-flop, and an output enable. The top 12
product terms are group ed i nto thr ee su m te rms, which are
used as shown in the macrocell diagram s.
Eight synchronous preset terms are distributed in a 2/4 pattern. The first four mac roc ell s s har e Pres et 0, t he nex t t w o
share Preset 1, a nd so on, end ing w ith th e last two ma crocells sharing Preset 7.
The 14 dedicated inputs an d their com plements use the
numbered positions in the global bus as shown. Each
macrocell provides six inputs to the global bus: (left to
right) feedback F2
(1)
true and false, flip-flop Q1 true and
false, and the pin true and false. The positions occupied by
these signals in the global bus are the six numb ers in the
bus diagram next to each macrocell.
Note: 1. Either the flip-flop input (D/T2) or output (Q2) may
be fed back in the ATV2500Bs.