1. Overview The calling number display service (CID service for short) is a new service item provided to the called telephone user. It refers to a service item that displays calling number, calling time and other calling identification information on the terminal device of the called user and stores it for the user to consult. This service has been successively opened in major cities in China.The basic method is that the exchange will exchange information such as calling number through frequency shift keying (FSK) or dual tone multi-frequency (DTMF) through the inter-office signaling system (such as No. 7) Pass to the terminal exchange, as shown in Figure 1. China adopts the FSK system, which is taken as an example in the following discussion. The specific timing of caller identification information transmission is shown in Figure 2. The calling number identification receiver HT9030 developed by HOLTEK is a low-power integrated circuit manufactured by CMOS technology. It can receive the physical layer signal that conforms to the Bell Center TR-NWT-000030 specification, and is mainly used in products that receive and display the calling number and related information sent by the exchange. The device can also provide low-voltage detection circuit, power-down circuit, carrier detection circuit and ringing detection circuit to facilitate system application. 2. Pin arrangement and pin function HT9030 adopts dual in-line 16-pin package. The pin arrangement and internal structure are shown in Figure 3. The functions of each pin are as follows: DOUT: When the CDET pin is at a low level, this terminal outputs a demodulated signal. The data stream includes alternating 1, 0, and 150 ms mark signals. The mark signal is located at the front of the data. At other times, the port remains in a high-impedance state. This paper address: http: // Erase your drawing image with the press of a button.
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The calling number display identification integrated circuit HT9030 mainly has the following characteristics:
â— BELL 202 FSK demodulation;
â— Ring detection input and output;
â— Carrier detection output;
â— Low voltage detection output;
â— Power-off working mode;
â— High input sensitivity;
â— Using 3.58MHz crystal oscillator or ceramic oscillator. 
VDD, VSS: positive power supply and ground respectively;
TIP, RING: Connect to the two ends of the telephone line respectively. When working, TIP and RING should be connected with the lead of the telephone line in series with 0.1μF capacitors to achieve DC isolation between the telephone lines;
RDET1: detect the ringing energy through the attenuation network and start the oscillator and ring current detection circuit;
RDET2: coupling the ringing signal to the ringing current detection circuit through the attenuation network;
LBIN: Low voltage detection input terminal;
RTIME: This end is connected to an RC network. Therefore, the voltage between the peaks of the ringing signal at this end is lower than 2.2V. It controls the internal power-on and activates local circuits to judge whether the incoming call is valid;
PDWN: When this terminal is high, the chip is in power-down mode; when it is low, the chip is activated;
X1, X2: external 3.58MHz crystal oscillator or ceramic oscillator;
LBPUT: When the voltage at the LBIN terminal is lower than the internal reference voltage, output high level, otherwise output low level;
RDET: When a valid ringing signal is detected, this port goes low. This pin can be powered on automatically when connected to the PDWN pin;
CDET: When a valid carrier frequency on the telephone line is detected, this port becomes low. The chip has a built-in delay circuit to allow instantaneous shift of the carrier frequency. This pin is connected to the PDWN pin and can be used for automatic power-on;
The chip is composed of a clock generation circuit, a ringing detection circuit, a power-down control circuit, an undervoltage detection circuit, and a BELL 202 FSK demodulation circuit. The function of the ring detection circuit is to detect the ring signal on the telephone line. When a valid ring current signal is detected, the 12 pin of the chip outputs a low level, and at the same time triggers the clock generation circuit and the power-down control circuit, so that the entire chip In working condition. Then, the BELL 202 FSK signal following the ringing current is input from pins 1 and 2 of the chip, and the calling number information is output from pin 14 through the amplifier, band pass filter, demodulator, and valid data detection circuit.
3. The interface circuit of the application circuit HT9030 and the single chip microcomputer is shown in Figure 4. The working process is as follows: When a calling user calls, the exchange sends a ringing signal to the called user through the telephone line. After the ring current signal passes through the DC isolation capacitors C3, C4, rectifier bridge, attenuation network R3, R4, R5, the on-chip oscillator is started via RDET1 and the signal is coupled to the ring current detection circuit in the chip. After the HT9030 detects the ring current signal, it outputs a low level at the RDET pin. When the MCU detects this signal, it sets the PDWN pin low and activates the HT9030. During the ringing interval, the exchange transmits the calling information to the called user in the form of FSK. The signal is coupled from C1, C2, R1, R2 to the ends of TIP and RING, and enters the chip decoding circuit. If the decoding is successful, CDET goes low and the decoded signal is output from the DOUT pin. After the MCU receives the calling number, it can be stored in the corresponding storage unit or displayed on the display. This article describes a typical application circuit. If you add some additional circuits, you can complete more complex functions, such as checking the information of missed calls, and the emergency assistance center can use this function to find the position of the party more effectively. 
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Calling number identification receiver HT9030 and its application
Calling number identification receiver HT9030 and its application