HT9320 datasheet(6/30 Pages) HOLTEK

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Pin Name I/O

Internal

Connection

Description

MODE

I/O

CMOS

IN/OUT

This is a three-state input/output pin, used for dialing mode

selection, either Tone mode or Pulse mode, 10pps/20pps

MODE=VDD: Pulse mode, 10pps

MODE=OPEN: Pulse mode, 20pps

MODE=VSS: Tone mode

During the pulse mode dialing, switching this pin to the tone

mode changes the subsequent digit entry to the tone mode.

When the chips are in tone mode, switching to the pulse mode

will also be recognized.

DTMF

CMOS OUT

This pin is active only when the chip transmits tone dialing

signals. Otherwise, it always outputs a low. The pin outputs

tone signals to drive the external transmitter amplifier cir-

cuit. The load resistor should not be less than 5kW.

HDI

CMOS IN

Pull-high

This pin is a schmitt trigger input structure. Active low. Ap-

plying a negative going pulse to this pin can toggle the HDO out-

put once.

An external RC network is recommended for input

debouncing. The pull-high resistance is 200kW typ.

HDO

CMOS OUT

The HDO is a CMOS output structure. Its output is toggle- con-

trolled by a negative transition on HDI. When HDO is toggled

high, PO keeps high to hold the line. The hold function can be re-

leased by setting HFO high or by an on-off hook operation or by

another HDI input. The HDO pin can directly drive the HT3810

series melody generator to produce a hold-line background mel-

ody. Refer to the functional description for the hold-line func-

tion.

HFI

CMOS IN

Pull-low

This pin is a schmitt trigger input structure. Active high. Ap-

plying a positive going pulse to HFI can toggle the HFO once

and hence control the hand-free function.

An external RC network is recommended for input

debouncing. The pull-low resistance of HFI is 200kW typ.

HFO

CMOS OUT

The HFO is a CMOS output structure. Its output is toggle-

controlled by a positive transition on the HFI pin. When HFO

is high, the hand-free function is enabled and PO outputs a

high to connect the line.

The hand-free function can be released by an on-off-hook oper-

ation or by another HFI input or by setting HDO high. Refer to

the functional description for the hand-free function opera-

tion.

DOUT

NMOS OUT

NMOS open drain output pin. It outputs the BCD code of the

dialing digits to the LCD driver chip (HT16XX series) or mC for

dialing number display. Refer to the functional description for

the detailed timing.

HT9320

July 21, 1999

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