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LS7222: DescriptionKEYPAD PROGRAMMABLE DIGITAL LOCK; File Size31KB，4 Pages; ManufacturerLSC/CSI; Websitehttps://lsicsi.com

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LS7222 Overview

KEYPAD PROGRAMMABLE DIGITAL LOCK

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LSI/CSI

LS7222

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

December 2002

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

A3800

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

• +4V to +15V operation (V

-Vss)

• 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.

7222-121102-1

CONNECTION DIAGRAM -TOP

VIEW

LSI

(-V)

RC-OSC

(+V)

CAP-K

LOCK DISPLAY

LOCK

LS7222

DISARM

ALARM

ARM

TAMPER

CAP-M

FIGURE 1

PROGRAM

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.

Program Mode

- The current Arm/Disarm/Duress codes may be

KEYPAD INTERFACE

- The four X inputs and four Y outputs are

altered to any value by initializing the Program mode. The steps designed for keypad interface (see Fig. 2). Since the X inputs have

involved for altering the codes are:

internal pull-ups, the maximum matrix size of 4 x 4 does not have

to be utilized. Because the Y outputs have open drains, more

1. Enter the current Disarm code causing the Disarm output to

than one LS7222 may share the same keypad.

go high.

During normal operation the LS7222 will scan the matrix looking for

2. Before the keypad entry enable time expires, enter the key

a switch closure. Once a closure has been detected, the internal

corresponding to matrix position X4 Y1 two times. This will

key debounce logic determines if a "valid" key has been pressed or

cause the Program Mode output to latch high, indicating that that if noise is just present. Only one valid input will be generated

the circuit is now in the Program mode. The keypad entry

with any key closure. The use of internal key debouncing and

enable timer is disabled during the Program mode.

Schmitt triggers on the inputs provides the LS7222 with very high

noise immunity.

3. Enter a 6-digit number from the keypad. The Program Mode

output will latch low, indicating that the new codes have suc-

TAMPER -

When a valid key has been detected by the LS7222,

cessfully been programmed. Of the 6 digits, the first 4 con-

the entry is compared against the appropriate reference in the inter-

stitute the Arm code; the first 3 and the 5th constitute the Dis- nal memory. If the requirements of digit value and code sequential

arm code and the first 3 and the 6th constitute the Duress

position are not fulfilled, the Tamper output will momentarily go

code. If an error is introduced or it is desired to change the

high; this indicates that an illegal code entry was attempted. The

codes before the 6th digit is typed, enter the key X4 Y3. This keypad entry enable timer and memory pointer will both be reset so

will reset the internal memory pointer of the LS7222 and a

that entry of the code can be attempted again.

new 6-digit number can be entered.

FUNCTION

Vss

RC-OSC

TABLE 1. PIN DESCRIPTIONS

DESCRIPTION

Supply voltage negative.

Determines the LS7222's internal clock frequency, which is used for keyboard scanning

and debounce. A resistor (to V

) and a capacitor (to Vss) connected to this input sets

the frequency.

3, 4, 5, 6

7, 8, 9, 10

X1, X2, X3, X4

Y1, Y2, Y3, Y4

PROGRAM MODE

CAP-M

TAMPER

ARM

The four X inputs and four Y outputs are designed to interface to a keypad matrix

whose maximum allowable size is 4 by 4.

This output goes high when the program mode is initiated. It resets to a low state after the

6-digit Arm/Disarm/Duress combination code has been programmed.

A capacitor connected between this input and Vss controls the duration of the Arm,

Disarm and Tamper outputs.

Whenever a key is entered that is not a valid code element, this output goes high for a

period determined by the capacitor on the CAP-M input.

This output generates an active high output every time the Arm code is entered,

irrespective of whether the circuit is currently in the disarm state or not. The duration of

this output is determined by the capacitor on the CAP-M input. When the Arm and Disarm

codes are identical , this output will occur on every other code entry.

ALARM

DISARM

When the Duress code is entered, this output latches high to enable an external alarm.

The Alarm output resets to a low state when the Arm code is entered again.

This output generates an active high output every time the Disarm code is entered,

irrespective of whether the circuit is currently in the armed state or not. The duration of

this output is determined by the capacitor on the CAP-M input. When the Arm and Disarm

codes are identical , this output will occur on every other code entry.

LOCK

When the Disarm code or the Duress code is entered, this output latches high. When the

Arm code is entered, the output latches low. If the Disarm or Duress code is entered

when the output is already high (i.e. already disarmed), the output remains unaffected.

Similarly, if the Arm code is entered when the output is already low (i.e. already armed), it

remains unchanged. An exception to this rule is when the Arm and Disarm code identical

in all 4 digits. In that situation, the output will toggle every time the code is entered.

LOCK STATUS

Functionally, this output is identical to the LOCK output, with the exception that its polarity

is reversed with respect to the LOCK output. This output is intended for driving a display

lamp to indicate the lock status.

7222-012901-2

CAP-K

A capacitor connected between this input and Vss sets the time limit for entering a 4 digit

code from the keypad. (6 digits when initiating the program mode.)

Supply voltage positive.

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