Philips Semiconductors

Product specification

PLUS405-37/-45

Programmable logic sequencers

(16

× 64 × 8)

1996 Nov 12

7

DETAILS FOR REGISTERS FOR PLUS405

STATE REGISTERS

J

K

Q

P

R

CLK

TO INIT LINE

TO AND

ARRAY

Detail B

19

INIT/OE

Detail A

Ps

OUTPUT REGISTERS

J

K

Q

P

R

CLK

TO INIT LINE

Detail C

Fn

FROM

PIN 1 CLK

FROM PIN 4

(I5/CLK)

Detail D

SP00254

COMPLEMENT ARRAY DETAIL

P63

P62

P2

P1

P0

A

B

C0

D

E

C1

C1

C0

TO OR ARRAY

SP00255

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 has 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.