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W91550DNH

13-MEMORY TONE/PULSE DIALER WITH LCD AND LOCK FUNCTIONS

Winbond 

W91550DN SERIES

Pin Description, continued

SYMBOL PIN

HFI , HFO 57, 58

LOCK

64

I/O

FUNCTION

I, O Handfree control pins. A low pulse on the HFI input pin toggles the

handfree control state.

Status of the handfree control is listed in the following table:

CURRENT STATE

Hook SW.

HFO

−

Low

On Hook

High

Off Hook

High

On Hook

−

Off Hook

Low

Off Hook

High

NEXT STATE

Input

HFO

HFI

High

HFI

Low

HFI

Low

Off Hook

Low

On Hook

Low

On Hook

High

Dialing

Yes

No

Yes

Yes

No

Yes

HFI pin is pulled to VDD by internal resistor.

Detailed timing diagram is shown in Figure 4.

I The LOCK pin is used to prevent "0" or "9" dialing under PABX

system long distance call control. When the first key input after reset

is "0" or "9", all the key inputs, including "0" or "9" key, become

invalid, and the chip generates no output.

The telephone is reinitialized by a reset.

The following table describes the functions of the LOCK pin:

LOCK PIN

Floating

VDD

VSS

FUNCTION

Normal dialing

"0", "9" dialing inhibited

"0" dialing inhibited

TEST

VLCD

CP, CN

37

59

60, 61

I In normal operation, pulling the TEST pin to VDD inhibits the single

tone. In testing operation, pulling the TEST pin to VSS enables a

single tone to be created by pressing two keys simultaneously, and all

of the timing parameters for pulse dialing are faster than in normal

operation.

I Power supply pin for LCD driver.

A 1µF capacitor is connected between VLCD and VSS.

I CP is the voltage control capacitor positive pin.

CN is the voltage control capacitor negative pin.

A 1 µF capacitor is connected between these two pins.

Publication Release Date: November 1997

-5-

Revision A3

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