LSI LS7222-S, LS7222 Datasheet

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 (VDD -Vss)

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

GENERAL DESCRIPTION:

The LS7222 is a programmable electronic lock imple­mented 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 4­digit 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. When­ever 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

LSI

CONNECTION DIAGRAM -TOP VIEW

VDD (+V)

CAP-K

LOCK DISPLAY

LOCK

DISARM

ALARM

TAMPER

CAP-M

PROGRAM

ARM

VSS (-V)

RC-OSC

X1

X2

X3

X4

Y1

Y2

Y3

Y4

FIGURE 1

LS7222

December 2002

7222-121102-1

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 [phone] FAX [phone]

LS7222

U

L

®

A3800

Program Mode - The current Arm/Disarm/Duress codes may be

altered to any value by initializing the Program mode. The steps
involved for altering the codes are:

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

2. Before the keypad entry enable time expires, enter the key
corresponding to matrix position X4 Y1 two times. This will
cause the Program Mode output to latch high, indicating that
the circuit is now in the Program mode. The keypad entry
enable timer is disabled during the Program mode.

3. Enter a 6-digit number from the keypad. The Program Mode
output will latch low, indicating that the new codes have suc­cessfully been programmed. Of the 6 digits, the first 4 con­stitute the Arm code; the first 3 and the 5th constitute the Dis­arm code and the first 3 and the 6th constitute the Duress
code. If an error is introduced or it is desired to change the
codes before the 6th digit is typed, enter the key X4 Y3. This
will reset the internal memory pointer of the LS7222 and a
new 6-digit number can be entered.

KEYPAD INTERFACE - The four X inputs and four Y outputs are
designed for keypad interface (see Fig. 2). Since the X inputs have
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
than one LS7222 may share the same keypad.

During normal operation the LS7222 will scan the matrix looking for
a switch closure. Once a closure has been detected, the internal
key debounce logic determines if a "valid" key has been pressed or
that if noise is just present. Only one valid input will be generated
with any key closure. The use of internal key debouncing and
Schmitt triggers on the inputs provides the LS7222 with very high
noise immunity.

TAMPER - When a valid key has been detected by the LS7222,
the entry is compared against the appropriate reference in the inter­nal memory. If the requirements of digit value and code sequential
position are not fulfilled, the Tamper output will momentarily go
high; this indicates that an illegal code entry was attempted. The
keypad entry enable timer and memory pointer will both be reset so
that entry of the code can be attempted again.

TABLE 1. PIN DESCRIPTIONS

PIN FUNCTION DESCRIPTION

1 Vss Supply voltage negative.
2 RC-OSC Determines the LS7222's internal clock frequency, which is used for keyboard scanning

and debounce. A resistor (to VDD) and a capacitor (to Vss) connected to this input sets

the frequency.

3, 4, 5, 6 X1, X2, X3, X4 The four X inputs and four Y outputs are designed to interface to a keypad matrix

7, 8, 9, 10 Y1, Y2, Y3, Y4 whose maximum allowable size is 4 by 4.

11 PROGRAM MODE 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.

12 CAP-M A capacitor connected between this input and Vss controls the duration of the Arm,

Disarm and Tamper outputs.

13 TAMPER 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.

14 ARM 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.

15 ALARM 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.

16 DISARM 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.

17 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.

18 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.

19 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.)

20 VDD Supply voltage positive.

7222-012901-2