Using the HT95R6x for CID Phones

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1 Using the HT95R6x for CID Phones D/N : AN0319E Introduction Holtek s new HT95R64 and HT95R65 devices are 8-bit CID Phone MCUs with a CPT function. The HT95R64/HT95R65 devices, with their internal DTMF Generator/Receiver, FSK Decoder and CPT Detector, are used in the CID phone and answering machine application area. In addition to supporting Bell 202 and ETSI V2.3 specifications, the internal FSK decoder also supports Ring and Line Reverse detection. The features of these two MCUs internal sources are shown in the following table. For these two devices, the internal PLL can shift the frequency up to 3.58MHz, 7.16MHz, 10.74MHz and 14.32MHz using a 32768Hz external crystal oscillator which is connected between the X1 and X2 pins as a system clock source. Note that with higher operating frequencies, higher operating voltages are required. When the system clock is 3.58MHz, the operating voltage range is 2.2V to 5.5V. If the CPT function is used, an external 32768Hz crystal oscillator must be connected between the CPTX1 and CPTX2 pins. This application describes how to use the HT95R65 internal funcions and external circuits to implement CID phone functions. 1

Operating Principle The phone circuits are not identical, but the basic structure generally includes a hook switch, a ringing circuit, a polarity conversion circuit, a dialing circuit and a speech

2 Operating Principle The phone circuits are not identical, but the basic structure generally includes a hook switch, a ringing circuit, a polarity conversion circuit, a dialing circuit and a speech circuit, etc. Off Hook Switch: used as a switching function. When the phone is off hook, the dialing and speech circuits are turned on for dialing and speech operations. When the phone is on hook, the dialing and speech circuits are turned off. Ringing Circuit: used to rectify and step-down 75V/25Hz ring signal voltage delivered from the exchange to supply power for the integrated circuits, and generate two alternating signals with different frequencies, which are ampified to drive the buzzer or speaker forming a ringtone. Polarity Conversion Circuit: used to convert the uncertain polarity voltage from the exchange into a fixed polarity voltage. No matter how the exchange is connected in, this circuit is able to convert the delivered power into one with required positive and negative polarity. Start-up Circuit: mainly composed of a transistor controlled by the hook switch. This circuit is used to maintain normal MCU operation during an off hook or on hook condition. When in an on hook condition, the MCU enters the sleep mode, when in an off hook condition, the MCU is woken up and enters the operating mode. Dialing Circuit: composed of an electronic switch, dialing keys and peripheral circuits. The main functions of this circuit are to deliver phone number signals, connect to the signal transmission circuit via the electronic switch, turn off the speech circuit during a dialing operation to avoid noise, and use each key to perform a corresponding function. Speech Circuit: composed of a transmitter circuit, a receiver circuit and an anti-sidetone circuit. The receiver circuit is used to amplify and process the calling signals from the other side, convert the voice message into sound using electronic components. The transmitter circuit is used to convert the speaker s voice into electrical signals, amplify and deliver them to the outside lines to the exchange. During speech, a phenomenon exists whereby the speaker can hear their own voice, which is called side tone. The anti-sidetone circuit eliminates the answering noise by controlling the receiver circuit. 2

3 Telephone Dialing Introduction There are two telephone dialing methods known as DTMF and Pulse. DTMF, is an abbreviation for Dual Tone Multi Frequency, which is widely used in telephone dialing applications. A DTMF signal consists of two frequencies, one from a low frequency group and one from a high frequency group. The low group includes 697Hz, 770Hz, 852Hz and 941Hz; the high group includes 1209Hz, 1336Hz, 1477Hz and 1633Hz. As each DTMF signal is composed of a low frequency and a high frequency source, their combination can generate a total of 16 signal types. Pulse dialing is a rotary dialing method where the number of pulses indicates the dialed digit. The HT95R65 includes a fully integrated DTMF generator, which can output the necessary 16 dual tones and 8 single tones on the DTMF pin. The DTMF generator clock source is fixed at 3.58MHz. Before using this module, the HT95R65 is required to operate in the normal mode, independent of whether the MCU system clock runs at 3.58MHz, 7.16MHz, 10.74MHz or 14.32MHz. The internal DTMFC register controls the DTMF Generator on/off status and the DTMF signal output. When the DTMF generator is on and the tone output is enabled, then when a value is written to the internal DTMFD register, the DTMF Pin will generate a corresponding DTMF signal. 3

4 CID Introduction CID is short for Calling Identity Delivery, meaning the calling identity is delivered and displayed. It is often known as Caller ID. A CID phone also includes FSK and DTMF decoder circuits based on ordinary phones, but gets its decoder information from the microcontroller, and then displays the calling information on an LCD. The American Bell Communication Institute has defined the protocol regarding the caller user name, the calling date, time and so on using FSK (Frequency-shift Keying) with Voice Band Data Communication modulation and demodulation technologies. Later on some European countries delivered this information using DTMF (Dual Tone Multi-frequency). Presently the CID FSK and DTMF technologies well defined at present. HT95R6x DTMF Recevier The HT95R6x devices contain a fully integrated DTMF receiver which will decode the DTMF frequency content of incoming analog DTMF signals. An internal operational amplifier is also supplied to adjust the input signal level. There is also a pre-filter function which is a band rejection filter to reject frequencies between 350Hz and 400Hz. The low group filter filters the low group frequency signal output, whereas the high group filter filters the high group frequency signal output. Each filter output is followed by a zero-crossing detector which includes hysteresis. The DTMF receiver is controlled by the internal DTRXC register, and the DTMF code is placed in the DTRXD register. DTRXC Register R_DV: DTMF data valid output flag. If R_DV=0, there is no valid DTMF tone received; if R_DV=1, then a valid DTMF tone has been received. R_INH: enable/disable the detection of tones representing the characters A, B, C and D. If R_INH=0, then this detection is enabled; if R_INH=1, the detection is disabled. R_PWDN: DTMF Receiver Power Down enable bit. If R_PWDN=0, the DTMF receiver is in the normal mode; if R_PWDN=1, the DTMF receiver is in the power down mode. 4

5 DTRXD Register HT95R6x FSK Decorder The HT95R6x devides contain a fully integrated FSK decoder which will decode the FSK frequency content of incoming analog FSK signals. The FSK decoder supports two CID specifications, Bell 202 and ETSI V2.3, as well as ring and line reversal detection. It also supports four interrupt sources to the peripheral interrupt vector, which are FSK raw data falling edge, ring detect or line reversal detect, FSK carrier detect and FSK packet data. The HT95R6x devices each have four registers related to the FSK decoder, FSKC, FSKS, FSKD and PERIC. FSKC Register FSKSEL: Select FSK packet data source. FSKSEL=1, DOUTC; FSKSEL=0, DOUT. CMSK: FSK carrier detect interrupt mask. CMSK=1, disable; CMSK=0, enable. RMSK: Ring or line reversal detect interrupt mask. RMSK=1, disable; RMSK=0, enable. FMSK: FSK packet data interrupt mask. FMSK=1, disable; FMSK=0, enable. F_PWDN: FSK decoder power down control. F_PWDN=1, power down mode; F_PWDN=0, normal mode. FSKS Register RINGF: Ring signal interrupt flag. This bit is read only and can not be modified by S/W. FSKF: FSK packet data interrupt flag. FSK=1, FSK packet data is received. DOUTC: FSK decoder cooked data output. This bit is read only and can not be modified by S/W. DOUT: FSK decoder raw data output. This bit is read only and can not be modified by S/W. CDETF: FSK carrier detect interrupt flag. CDETF=1, valid FSK 0, 1 signals; CDETF=0, no valid FSK 0, 1 signals. RDETF: Ring or line reversal detect interrupt flag. RDETF=1, ring or line reversal; RDETF=0, no ring or line reversal. 5

6 FSKD Register The FSKD register is used to store the decoded FSK packet data. PERIC Register FSKDF: FSK raw data falling edge interrupt flag. DTMFF: DTMF receiving interrupt flag. EFSKDI: FSK raw data falling edge interrupt control bit. EFSKDI=1, enable; EFSKDI=0, disable. EDTMFI: DTMF receiving interrupt control bit. EDTMFI=1, enable; EDTMFI=0, disable. CPT Function Introduction CPT, which is the Call Progress Tone, is a group of audio tones delivered from the exchange to the caller which is used to indicate the status of the call which includes Dial Tone, Busy Tone, Ring-back Tone and Recorder Tone, etc. The HT95R6x devices contain a fully integrated CPT detector, which can be used for Auto-dialing systems in telecom applications. After dialing, the system will determine the status of the called side according to the received CPT signal and execute an appropriate operation. For example, if a Busy Tone is received, it means that the called side is executing an active call so the caller should dial again later. When the CPT detector detects a CPT signal, its CPTENV pin will generate an envelope signal. The MCU will use a common I/O pin to detect the time of the high and low levels which stand for the tone on and off time, and then determine the CPT signal type according to the CPT specifications. For more details, refer to the application note HT95R6x CPT (Call Progress Tone) Decoder Function on the Holtek website. Phone Power Supply Touch-tone phone power is supplied by the exchange. When the phone is on hook, the voltage is usually 48V for the stored program controlled exchanges, 60V for the crossbar exchanges or 24V for other exchanges. When the phone is ringing, the exchange will deliver a 75V/25Hz ring signal. After the phone is off hook, the voltage is between the range of 6V to 12V depending on the line length and the phone quality. According to the specifications of the automatic telephone set, GBT Standard, the leakage current in the on hook status should be less than 25uA. When the phone is off hook, the exchange usually provides a 20~30mA current for the phone which will not affect normal speech. To follow the specifications, when the phone is on hook, an external power such as a battery is required to ensure the current obtained from the exchange is less than 25uA. After the phone is off hook, it will switch to have its power-supplied by the exchange. 6

HT95R6x Phones Power supply This application uses the HT95R65 internal DTMF receiver and FSK decoder to decode the analog signal frequency content. The system clock for these two modules is 3.

According to the specifications, with the above features, the HT95R6x CID phones require an external battery to supply power for the MCU.

7 HT95R6x Phones Power supply This application uses the HT95R65 internal DTMF receiver and FSK decoder to decode the analog signal frequency content. The system clock for these two modules is 3.58MHz, and the MCU should work in normal mode. A complete FSK or DTMF CID display lasts for several seconds during which time the whole power consumption is usually 3~4mA. According to the specifications, with the above features, the HT95R6x CID phones require an external battery to supply power for the MCU. Application Circuit HT95R65 CID Phones Block Diagram The HT95R65 CID phone block diagram is shown as follows: This phone is composed of the phone MCU HT95R65, an over voltage protection circuit, a ring circuit, a polarity conversion circuit, a start-up circuit, a dialing circuit, a CID decoder circuit, a hand speech circuit, a hands-free speech circuit, an LCD display circuit and a power circuit. Over Voltage Protection Circuit: used to avoid phone damage caused by high voltage transients on the external lines to maintain normal phone operation. Polarity Conversion Circuit: used to convert the reverse polarity DC voltage into a fixed polarity DC voltage. Ring Circuit: used to process the 75V/25Hz signal to generate a ring to inform user to answer the phone. 7

8 Start-up Circuit: used to control the MCU operating mode. When there is no call, the MCU enters the Halt mode; if the phone is off hook or the hands-free key is pressed, the MCU will be woken up. Dialing Circuit: the MCU uses the DTMF generator to process the dialed phone number, then generates a DTMF signal on the DTMF pin and outputs it to the outside line for the exchange to idendity. CID Decoder Circuit: it uses the internal DTMF receiver and the FSK decoder to decode the FSK and DTMF signals. Hands Speech Circuit: used to complete the transmitter/receiver conversion to achieve communication between two sides. This circuit is mainly composed of a communication IC, a peripheral anti-sidetone circuit and a noise reduction circuit. When the phone is communicating with the outside, the frequency of the voice signal is usually between 300Hz and 3400Hz, which is implemented using a specific IC, the TEA1062, and peripheral components. Hands-free Speech Circuit: used to complete the transmitter/receiver conversion to achieve communication between two sides using a specific IC, the MC34018, and peripheral components. CPT Decoder Circuit: uses the internal CPT detector to detect the call progress tone. LCD Display Circuit: the MCU uses an I 2 C interface to communicate with the LCD driver IC, the HT16C24, which is used to display the CID and dialed data. Flash Memory IC: it is used to store the voice data and phone number. 8

9 HT95R65 CID Phone Application Circuit 9

10 Functions and S/W Flowcharts HT95R65 CID Phone Functions The HT95R65 CID phone application circuit works together with the source code placed in the attachment section to implement the following functions. FSK/DTMF dual formats automatically compatible The system can automatically identify the CID data type, FSK or DTMF, and display it on the LCD. 8 groups of CID data display and storage Supports 8 groups of CID data storage. 8 groups of dialed data display and storage Supports 8 groups of dialed data storage. Dialed data check/redial Pressing the Dialed key can check the dialed phone number. Then pressing the Redial key will dial this checked number. CID data check/redial Pressing the Up key can up-check the caller number, pressing the Down key can down-check the caller number, and pressing the Redial key will dial the checked number. CID/Dialed data delete When checking the CID or dialed number, press the Delete key to delete the current CID or dialed number. Automatically dialing simulation Press the Set key, the LCD will then display SET. Input a phone number and press the Set key, then the phone number will be stored in the Flash memory, and the LCD will display SUCCESS. After pressing the Calculator key, the phone number stored in the Flash will be automatically dialed and the CPT function will be enabled. If three busy tones are detected, the system will automatically be on hook. If a ring-back tone is detected, it means that the call is connected. After 4s, the MCU will use an SPI interface to read voice data from the Flash IC and play it out using its internal 12-bit DAC. 10

11 HT95R65 CID Phone S/W Flowchart and Description Main S/W Flowchart and Description 11

12 Main flowchart description: After power-on, the program will clear the RAM, initialize the I/O ports and SFRs, and initialize the HT16C24 via an I 2 C interface. After initialization, the program will enter the main flowchart. Firstly, enter the key scanning module, then call the off hook detecting module and the dialing module. And then check whether phonetask&keytask=1 or not, if yes, enter the key processing module. Check whether phonetask&callidtask=1 or not, if yes, enter the CID processing module. Check whether phonetask&timetask=1 or not, if yes, enter the time display and LCD update module. Check whether phonetask&cpttask=1 or not, if yes, enter the CPT detecting module. Check whether phonetask&halttask=1 or not, if yes, enter the Halt mode; if no then turn back to the key scanning module to continue the cycle. The interrupt processing module is mainly to implement the ringing detecting, FSK and DTMF decoding. In the entire flowchart, the system implements functions like time and date display in the standby mode; executing the related system settings and functions according to the key input. When a call is received an interrupt is generated. The interrupt processing module will determine the received data type to be FSK or DTMF, then decode the data and deliver it to the LCD. 12

13 FSK CID Message Receiving Flowchart and Description FSK Receiving Subroutine FSK_Interrupt=0 FSK_count==0 &&Fskd==04? Y Valid_FSK=1 N Valid_FSK==1? Y Clear LCD Store FSK data FSK_count++ N N FSK_count equals to FSK data length? Y Valid_FSK=0 Display FSK data RET When FSK_Interrupt=1, the FSK data receiving subroutine is called. Firstly, clear the FSK_Interrupt flag, then check whether the FSK data is valid or not. The single data message format, SDMF, is 04H + message length + year, month, date, hour, minute, second + caller number. If the first data received is 04H, it means that this FSK data is valid and data receiving starts. Clear the LCD, store the FSK data in FSK_Data. Check whether FSK_count equals to the FSK data length, if yes, data receiving ends. Clear the valid_fsk flag and display the FSK data. This application program does not support the MDMF, Multiple Data Message Format. 13

14 DTMF CID Message Receiving Flowchart and Description DTMF Receiving Subroutine DTMF_Interrupt=0 Y Valid_DTMF==0? N Dtrxd>10 dtrxd==0? Dtrxd>10 dtrxd==0? N Store DTMF data Y Y Valid_DTMF=1 Clear LCD Valid_DTMF=0 Display DTMF data N RET When DTMF_Interrupt=1, the DTMF data receiving subroutine is called. Firstly, clear the DTMF_Interrupt flag, and then check the Valid_DTMF flag. If Valid_DTMF=0, then check the first received data, if it is one of six head identifiers, A, B, C, D, * or #, set valid_dtmf=1, clear the LCD and exit the subroutine. When the next DTMF data arrives, Valid_DTMF=1, check the received DTMF data, if it is not one of six tail identifiers, A, B, C, D, * or #, store this DTMF data. If the received DTMF data is a tail idenditier, then the DTMF data receiving ends. Clear the Valid_DTMF flag and display the DTMF data. Note: The DTMF data head identifiers supported by this application program are A, B, C, D, * and #; The DTMF data tail identifiers supported by this application program are A, B, C, D, * and #. 14

15 DTMF Dialing Flowchart and Description The DTMF dialing subroutine is used to dial phone numbers. When dialing a phone number, the btoneon flag is set high, the DTMF generator and Timer1 are enabled, the _tone flag is set high, and the DTMF pin starts to deliver a DTMF signal which lasts 80ms. If the DTMF pin delivers continuous signals, the interval time between two adjacent DTMF signals is 80ms. After each DTMF signal is delivered, DialNumIndex will increase by one. If DiaNumIndex>=length, it means that the DTMF signal has been delivered. Then store the dialed phone number and the calling time. 15

16 CPT Detecting Flowchart and Description The CPT detecting subroutine is used to detect phone signals such as Busy Tone, Ring-back Tone, etc. The subroutine uses the timer to calculate the time of the CPT envelop signal high and low level. P_CPTENV stands for the current status of the CPTENV pin; benv_value stands for the last status of the CPTENV pin. Both High_count and Low_count will increase by one every 20ms. If benv_value==0&& P_CPTENV==1, which indicates a signal rising edge, the value of CPT_count is given to Low_count. Check the values of High_count and Low_count, which respectively stands for the high level time and low level time. If both High_count and Low_count values are between 15 and 19, namely 0.35s high and 0.35s low, it indicates a Busy Tone, bbusytone will be set high. If benv_value==1&& P_CPTENV==0, which indicates a signal falling edge, then go on to check High_count value, if it is between 47 and 53, namely 1s high, it indicates a Ring-back Tone, bringbacktone will be set high. Busy Tone: when the caller hears a beep, beep, beep sound with 0.35s ring and 0.35s off, it is a Busy Tone which means that the line is busy or the called side is on an active call. Ring-back Tone: after dial the called number, if the caller hears an intermittent sound like beep_beep_ with a 1s ring and 4s off. This is a Ring-back Tone which indicates that the called phone is ringing and waiting for an answer. 16

17 Conclusion This application shows how the HT95R65 is used to implement CID phone functions and provides the user a deeper understanding of the HT95R6x Phone MCUs. Attachments Source Code HT95R65_CID_Phone_Code(AN).zip Schematic HT95R65_CID_Phone_SCH(AN).zip 17

The HT95R5x/6x FSK Decoder Functions

The HT95R5x/6x FSK Decoder Functions D/N:AN0228E Introduction A CID phone is used for Caller Identification, also known as caller ID, and is a telephone service provided by telecommunication companies