PLUS405-55A データシートの表示（PDF） - Philips Electronics

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PLUS405-55A

Programmable logic sequencer (16 × 64 × 8)

Philips Electronics 

Philips Semiconductors Programmable Logic Devices

Programmable logic sequencer

(16 × 64 × 8)

Product specification

PLUS405-55

DETAILS FOR REGISTERS FOR PLUS405

19 INIT/OE

Detail A

OUTPUT REGISTERS

TO INIT LINE

J

Q

Fn

P

K

R

CLK

STATE REGISTERS

J

Q Ps

P

K

R

CLK

TO INIT LINE

TO AND

ARRAY

FROM PIN 4

(I5/CLK)

Detail B

FROM

PIN 1 CLK

Detail C

COMPLEMENT ARRAY DETAIL

P63 P62

P2 P1 P0

C0

C1

Detail D

A

B

D

E

C1

C0

TO OR ARRAY

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 fed

back to the AND array (NOR). 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 reset the state machine to a

known state. Without the Complement Array,

one would have to generate product terms for

all unknown or illegal states. With very

complex state machines, this approach can

be prohibitive, both in terms of time and

wasted resources.

Note that the PLUS405 sequencers have 2

Complement Arrays which allow the user to

design 2 independent Complement functions.

This is particularly useful if 2 independent

state machines have been implemented on

one device.

Note that use of the Complement Array adds

an additional delay path through the device.

Please refer to the AC Electrical

Characteristics for details.

October 22, 1993

185

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