PROGRAM MODE

The current Primary/Secondary/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 Secondary code causing the Lock 2 output

to toggle.

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 Primary code; the first 3 and the 5th constitute

the Secondary 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

LS7223 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 by 4 does not have to be utilized.

During normal operation, the LS7223 will scan the matrix look-

ing 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 LS7223 with very high noise immunity.

TAMPER

When a valid key has been detected by the LS7223, 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 LS7223's internal clock frequency, which is used for keypad scanning and

frequency. With a 1.5M

Ω resistor and a 100pF capacitor, the internal frequency is typically

10KHz and the internal anti-bounce is typically 25ms.

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 Primary/Secondary/Duress combination code has been programmed.

12

CAP-M

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

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

MOMEMTARY

This output generates an active high output every time the Primary code is entered. The

duration of this output is determined by the capacitor on the CAP-M input.

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 Primary code is entered again. This output pow-

ers-up to a low state.

16

LOCK 2

Whenever the Secondary code is entered, this output toggles. The output powers-up into a

low state.

17

LOCK1

When ever the Primary code or the Duress code is entered, this output toggles. The output

powers-up into a low state.

18

LOCK STATUS

Functionally, this output is identical to the Lock 1 output, with the exception that its polarity is

reversed with respect to the Lock 1 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

Supply voltage positive.

7223-013001-2