HT95LXXX
Rev. 1.20
25
May 26, 2004
Dialer I/O Function
Aspecial dialer I/O circuit is built into the telephone controller for dialing application. These specially designed I/O cells
allows the controller to work under a low voltage condition that usually happens when the subscriber s loop is long.
Dialer I/O pin function:
Name
I/O
Description
XMUTE
NMOS Output
XMUTE pin output is controlled by software. This is an NMOS open drain structure
pulled to VSS during dialing signal transmission. Otherwise, it is an open circuit.
XMUTE is used to mute the speech circuit when transmitting the dialer signal.
DNPO
NMOS Output
DNPOpinisanNMOSoutput,usuallybymeansofsoftwaretomake/breaktheline.
This pin is only controlled by software.
PO
CMOS Output
This pin is controlled by the HKS, HFI and HDI pins.
When PO pin is high, the telephone line is make.
When PO pin is low, the telephone line is break.
HKS
Schmitt Trigger
Input
This pin controls the PO pin directly.
This pin is used to monitor the status of the hook-switch and its combination with
HFI/HDI can control the PO pin output to make or break the line.
A rising edge to HKS pin will cause the dialer I/O to be on-hook status and generate
an interrupt, its vector is 18H.
A falling edge to HKS pin will cause the dialer I/O to be off-hook status and clear HFO
andHDOflagsto0.Thisfallingedgewillalsogenerateaninterrupt,itsvectoris18H.
HDO
CMOS Output
Supported for HT95L400/40P, HT95L300/30P, HT95L200/20P, HT95L100/10P
This pin is controlled directly by HDI, HKS and HFI pin.
When HDO pin is high, the hold-line function is enabled and PO outputs a high signal
to make the line.
HDI
Schmitt Trigger
Input
Supported for HT95L400/40P, HT95L300/30P, HT95L200/20P, HT95L100/10P
AlowpulsetoHDIpin(hold-linefunctionrequest)willclearHFOto0andtoggleHDO
and generates an interrupt, its vector is 18H.
This pin controls the HFO and HDO pins directly.
This pin is functional only when the line is made, that is, off-hook or hand-free
(PO output high signal).
HFO
CMOS Output
This pin is controlled directly by HFI, HDI and HKS pins.
When HFO pin is high, the hand-free function is enabled and PO outputs a high
signal to make the line.
HFI
Schmitt Trigger
Input
A high pulse to HFI pin (hand-free function request) will clear HDO to 0 and toggle
HFO and generates an interrupt, its vector is 18H.
This pin controls the PO, HFO and HDO pins directly.
The following are the recommended circuit for HFI and HDI pins.
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