EM91440 SERIES

TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE

AND DUAL-TONE MELODY GENERATOR

3

* This specification are subject to be changed without notice.

10.1.1997

FUNCTIONAL BLOCK DIAGRAM

COL1

COL2

COL3

COL4/KT

COL5

XIN

XOUT

ROW1

ROW2

ROW3

ROW4

HFO HDO

XMUTE

Keyboard

interface

(column)

Oscillator

Keyboard

interface

(Row)

Output circuit

Memory

(Melody)

Timing/Control circuit

Input circuit

Pulse

generator

latch

&

decoder

D/A

converter

Row/Column

programming counter

DTMF

PO

HKS

HFI

VDD

DRING

VDD

RMUTE

SDO

PIN DESCRIPTIONS

Symbol

Function

ROW1~ROW4

Keyboard scan pins of row group. In idle state (HKS is “High” and HFO is “Low”),

these pins stay “High impedance” level to prevent power consumption. Otherwise,

these pins switch to “High” level for detecting keyboard entry. These pins will output

600 Hz signal while keyboard is scanning.

COL1~COL3 and COL5

Keyboard scan pins of column group. In idle state, these pins stay “High impedance”

level. Otherwise these pins switch to “Low” level for detecting keyboard entry. These

pins will output 600 Hz signal while keyboard is scanning.

COL4/KT

The fourth column group pin of the keyboard that also provides the keytone output

. Normally, this pin stays “Low” level for detecting keyboard entry. After a valid

keyboard entry, this pin will output keying confirmation tone that is 600 Hz signal and

30 ms duration. To prevent signal interference, while DTMF issue, it will disable key

tone output except function key.

XIN and XOUT

Oscillator input and output pins. A 3.579545 MHz crystal or ceramic resonator must

be crossed connection to XIN and XOUT pins which generate system clock.

XMUTE

The Tone/Pulse MUTE signal output pin that is NMOS open-drain output structure.

This pin will switch to “Low” level during Tone/Pulse dialing and hold function .

Otherwise, this pin stays “High impedance” level.

V

DD

and V

SS

Positive and negative power supply input pins. Recommended operating voltage from

2.0Vdc to 5.5Vdc.

HFI

Handfree inputs pin which accepts falling edge signal to turn “on” or turn “off”

handfree function. This pin is hysteresis input structure and built-in pull up resistor

(typically 200 Kohms).

HFO

Handfree outputs pin that is designed to control telephone line for on-hook dialing or

control speakerphone circuit for handfree conversation. When handfree function is

executed, this pin will switch to“High”. Otherwise, this pin stays “Low” level.

DTMF

The DTMF (Dual Tone Multi-Frequency) and music signals output pin. Normally,

this pin stays “Low” level. In Tone dialing mode, this pin will output DTMF signal

that is corresponding to keyboard 0 .. 9, * and # keys. Beside this, in the line hold

duration, this pin will issue dual-tone music for telephone line.