PLC42VA12 Datasheet, PDF (13/20 Pages) NXP Semiconductors – CMOS programmable multi-function PLD 42 × 105 × 12

Philips Semiconductors Programmable Logic Devices
CMOS programmable multi-function PLD
(42 × 105 × 12)
Product specification
PLC42VA12
OUTPUT CONTROL OPTIONS
OMC
CONFIG.
OPTIONS
TO
AND ARRAY
OE CONTROL FUSE
FROM OE PIN
CODE
A
OE
M
E_n FUSE
FROM OE PIN
CODE
A
Output Enable Control Options
Similar to the Clock Options, the Output
Enable Control for each OMC can be
connected either to an external source
(I9/OE, pin 13) or controlled from the AND
array (P-terms DM_n). Each Output can also
be permanently enabled.
Output Enable control for the two
bi-directional I/O (B pins 10 and 11) is from
the AND array only (P-terms DB0 and DB1
respectively).
DM
OMC
CONFIG.
OPTIONS
TO
AND ARRAY
OE FUSE
FROM P-TERM CONTROL
CODE
•
M
E_n FUSE
FROM P-TERM CONTROL
CODE
A or 0
OMC
CONFIG.
OPTIONS
TO
AND ARRAY
OE CONTROL FUSE
ALWAYS ENABLED
CODE
A
M
E_n FUSE
ALWAYS ENABLED
CODE
0
COMPLEMENT ARRAY DETAIL
P₆₃ P₆₂ P₆₁
P₁ P₀ F_C LM_n
PM_n RM_n
C0
A
B
D
E
C0
TO OR ARRAY
TO OMCs AND BIDIRECTIONAL I/O
Notes on page 87.
Complement Array Detail
The complement array is a special sequencer
feature that is often used for detecting illegal
states. It is also ideal for generating
IF-THEN-ELSE logic statements with a
minimum number of product terms.
The concept is deceptively simple. If you
subscribe to the theory that the expressions
(/A * /B * /C) and (A + B + C) are equivalent,
you will begin to see the value of this single
term NOR array.
The complement array is a single OR gate
with inputs from the AND array. The output of
the complement array is inverted and fedback
to the AND array (NOR function). The output
of the array will be LOW if any one or more of
the AND terms connected to it are active
(HIGH). If, however, all the connected terms
are inactive (LOW), which is a classic
unknown state, the output of the complement
array will be HIGH.
Consider the product terms A, B and D that
represent defined states. They are also
connected to the input of the complement
array. When the condition (not A and not B
and not D) exists, the Complement Array will
detect this and propagate an Active-High
signal to the AND array. This signal can be
connected to product term E, which could be
used in turn to preset the state machine to
known state. Without the complement array,
one would have to generate product terms for
all unknown or illegal states. With very
complex state machines, such an approach
can be prohibitive, both in terms of time and
wasted resources.
October 22, 1993
85