KEYPAD PROGRAMMABLE DIGITAL LOCK

FEATURES:

• Stand alone lock logic

• 38416, 4-digit combinations

• 3 different user programmable codes

• Momentary and static lock control outputs

• Internal key debounce circuitry

• Tamper detection output

• Status outputs

• Low current consumption

• LS7222 (DIP), LS7222-S (SOIC)- See Figure 1

GENERAL DESCRIPTION:

The LS7222 is a programmable electronic lock imple-

mented in a monolithic CMOS integrated circuit. The circuit

contains all the necessary memory, decoder and control

logic to make a programmable "keyless" lock system to

control electro-mechanical locks. Input is provided by a

matrix keypad whose maximum allowable size is 4 x 4.

The LS7222 can be programmed to recognize 3 different

codes: one to lock (Arm), one to unlock (Disarm), and one

to unlock and trigger an alarm (Duress). Programming is

done via the keypad inputs. Any entry from the keypad

(when not in the program mode) which does not match one

of the 3 programmed codes causes the Tamper output to

become active.

The monolithic, low power CMOS design of the LS7222

enables it to be designed into typical battery backed-up and

automotive type security systems.

DETAILED DESCRIPTION:

CODES - There are 3 different function codes which the

LS7222 can store in memory. Each code consists of a 4-

digit number which must be entered in exact sequence and

before the keypad entry enable time expires. The 3 codes

and their functions are explained below.

1. The Arm code, when entered from the keypad,

causes the Lock output to latch low and the Arm output

to momentarily go high. Whenever power is first

applied to the LS7222, the circuit defaults to the Arm

code corresponding to the keys X1 Y1, X1 Y2, X2 Y2,

X2 Y1. The code can then be altered to any other 4

digit code by entering the Program Mode and keying in

the new code.

2. The Disarm code, when entered from the keypad,

causes the Lock output to latch high and the Disarm

output to momentarily go high. The first 3 digits of the

Disarm code must be identical to the first 3 digits of the

Arm code; the 4th digit may or may not be identical for

the two codes. When the two codes are the same in all

4 digits, i.e. the same code is chosen for arming and

disarming, the entry of the code will cause the Lock

output to toggle. This means that if the output was high

(unlocked) it will go low (locked) and vice-versa. When-

ever power is first applied to the LS7222, the circuit

defaults to the Disarm code corresponding to the keys

X1 Y1, X1 Y2, X2 Y2, X1 Y1. The code can then be

altered by entering the Program mode.

3. The Duress code, when entered from the keypad,

causes the Lock output to latch high and the Disarm

output to momentarily go high; at the same time the

Alarm output will latch high to enable an external alarm.

The first 3 digits of the Duress code must be identical to

the first 3 digits of the Arm and Disarm codes; the 4th

digit must be different to activate the Alarm output.

Whenever power is first applied to the LS7222, the

circuit defaults to the Duress code corresponding to the

keys X1 Y1, X1 Y2, X2 Y2, X1 Y2. The code can then

be altered the same way as the other two codes.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

CONNECTION DIAGRAM -TOP VIEW

CAP-K

LOCK DISPLAY

LOCK

DISARM

ALARM

TAMPER

CAP-M

PROGRAM

ARM

RC-OSC

X1

X2

X3

X4

Y1

Y2

Y3

Y4

FIGURE 1

December 2002

7222-121102-1

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747

(631) 271-0400 FAX (631) 271-0405

LS7222

UL

®

A3800