LSI/CSI
UL
®
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
DD
-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
SS
(-V)
1
RC-OSC
X1
X2
X3
X4
Y1
Y2
Y3
2
3
4
20
V
DD
(+V)
19
CAP-K
18
LOCK DISPLAY
17
LOCK
LS7222
5
6
7
8
9
16
DISARM
15
ALARM
14
ARM
13
12
TAMPER
CAP-M
Y4
10
FIGURE 1
11
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.
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