JPH0946384A - Demodulation circuit of caller's id signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demodulation circuit of a caller's ID signal which is inexpensive and is reduced the load on a main microcomputer. SOLUTION: This circuit is provided with a waveform shaping circuit 33 shaping an FSK signal into a rectangular wave signal and a one-chip microcomputer 34 to which the rectangular wave signal is supplied. In this one-chip microcomputer 34, the value of binary data is discriminated by measuring the time length of each cycle of the rectangular wave signal and this discrimination result is held in a RAM. By the request from the main microcomputer 20, the held discrimination result is transferred to the main microcomputer 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cola ID signal demodulation circuit.

[0002]

2. Description of the Related Art One of the functions in a telephone system is called a cola ID function. This cola ID function has been put to practical use in countries such as the United States, Canada, and the United Kingdom.
This function notifies the telephone number (line number) of the calling telephone.

To realize this cola ID function,
When calling the telephone of the called side by the ringer signal, binary digital data indicating the telephone number of the calling side (hereinafter,
A "caller ID signal") is formed at the central office. Then, for example, as shown in FIG. 5A, during the period TCI between the period T1 of the first ringer signal and the period T2 of the second ringer signal, the caller ID signal SCI is transmitted to the called telephone. Sent.

In this case, the cola ID signal SCI itself is a binary signal as described above, but it is converted into an FSK signal at the time of transmission, and is sent at 2200 Hz when the bit of the signal SCI is "0". When it is "1", it is set to 1200Hz.

Then, as shown in FIG. 5B, the cola ID
In the signal SCI, "0" and "1" are repeated for the first 250 msec period, and "1" is continued for the following 192 msec period, followed by main data. Is composed of a plurality of words W1 to WN, and each word is 10 bits long.
As shown in FIG. 5C, in each word, the first bit and the last bit are the start bit and the stop bit, and the 8 bits sandwiched between the start bit and the stop bit are the net data.

8 in the first word W1
The bit has a fixed value of 80H (“H” indicates a hexadecimal value), and 8 bits of the second word W2 indicate the number of the following words W3 to WN−1. Each 8 bits of the words W3 to WN-1 after the th are the ASCII code to indicate the telephone number of the calling side. Also, 8 bits of the last word WN are used as the checksum of the previous words W1 to WN-1.

Since the cola ID signal SCI is constructed as described above, if the cola ID signal SCI is taken out at the called telephone, the calling telephone, that is, the caller can be known. You can

[0008]

By the way, a dedicated demodulation IC has been developed as a demodulation circuit for the above cola ID signal SCI. Then, according to the demodulation IC, when the signal shown in FIG. 5A is supplied, demodulated data such as a telephone number is output in real time in series.

Therefore, the main microcomputer can display the telephone number of the calling party only by converting the data output from the demodulation IC into display data and supplying the display data to a display element such as an LCD. it can.

However, the demodulation IC is a dedicated IC
It is expensive because of the fact that it is, and that it has a built-in high-order filter circuit.

When the signal for demodulation shown in FIG. 5A is supplied, the demodulation IC outputs data such as demodulated telephone numbers in real time. Therefore, the main microcomputer for receiving the data has other functions. Even while realizing the above, it is necessary to preferentially receive and process the output data, and the software design becomes complicated or difficult.

The present invention is intended to solve such a problem.

[0013]

Therefore, according to the present invention, the FS is performed by the binary data indicating the telephone number and the like while being sent to the gap of the ringer signal at the time of the incoming call.
A demodulation circuit for demodulating the binary data from a K-modulated FSK signal, comprising a waveform shaping circuit for shaping the FSK signal into a rectangular wave signal, and a one-chip microcomputer to which the rectangular wave signal is supplied. Then, in this one-chip microcomputer, the value of the binary data is determined by measuring the time length of each cycle of the rectangular wave signal, and the determination result is held in the RAM so that it can be read from the main microcomputer. According to a request, the cola ID signal demodulation circuit is configured to transfer the held determination result to the main microcomputer.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 indicates a telephone line, and reference numeral 10 indicates a telephone having a cola ID function.

Then, in the telephone 10, the line 1 is
While being connected to the speech network circuit 13 through the protection circuit 11 and the interface circuit 12,
A transmitter 14 and a receiver 15 are connected to the speech network circuit 13. In this case, the interface circuit 12 has a hook switch that opens and supplements the line 1, and the speech network circuit 13 has a 2-wire / 4-wire conversion circuit and a muting circuit.

During a call, the voice signal from the transmitter 14 is sent to the line 1 through the signal line of the speech network circuit 13 → the interface circuit 12 → the protection circuit 11, and the voice signal of the other party is sent from the line 1. It is supplied to the handset 15 through the signal line of the protection circuit 11 → the interface circuit 12 → the speech network circuit 13.

Further, reference numeral 20 indicates a main microcomputer, and various operation keys 21 such as dial keys and the handsets 14, 15 are provided on the microcomputer 20.
A switch 22 which is on / off controlled by on-hook / off-hook of the above, and a dial signal (dial pulse or dial tone signal) forming circuit 23 are connected. The on / off hook of the interface circuit 12 is controlled according to the output of the switch 22, and the dial signal is output from the forming circuit 23 according to the operation of the dial key of the key 21, and the dial signal is transmitted through the interface circuit 12. It is sent to line 1.

Further, a ringer signal detection circuit 24 is connected to the signal line between the protection circuit 11 and the interface circuit 12, and the detection output is supplied to the ringer 25 and the microcomputer 20.
In addition, the microcomputer 20 includes a drive circuit 2
A display element, for example, the LCD 27 is connected through 6.

In the present invention, the cola ID
The demodulation circuit 30 for the signal SCI is configured as follows, for example. That is, at the time of incoming call, the ringer signal and the FSK signal modulated by the cola ID signal SCI are obtained in the signal line between the protection circuit 11 and the interface circuit 12 in the format shown in FIG. 5A. But,
The rectangular wave signal S33 is supplied to the waveform shaping circuit 33 through the signal lines of the high pass filter 31 and the low pass filter 32, and this signal S33 is supplied to the microcomputer 34.

As shown in FIG. 2, for example, the microcomputer 34 includes a CPU 41, a ROM 42 in which a program is written, a work area RAM 43, a plurality of input / output ports 44, a voltage comparison circuit 45, a hardware timer 46, Latch 47 for interrupt control is 1
It is a chip IC. In addition, the ROM 42
Is provided with, for example, a routine 100 shown in FIG. 3 as a part of the program.

Then, the signal S33 is supplied to the comparison circuit 45, and the voltage VREF supplied as the reference voltage to the operational amplifiers forming the filters 31, 32 and the waveform shaping circuit 33 is supplied to the comparison circuit 45. . In this way, the timer 46 is driven by the output of the comparison circuit 45 each time the signal S33 rises and falls, and the time length of the half cycle period is measured for each half cycle of the signal S33.

Further, the signal S is sent to the microcomputer 34.
When 33 is supplied, the CPU 41 is interrupted and the processing of the routine 100 is started.
The subsequent interrupt is prohibited by the latch 47 until the processing of 00 is completed.

An example of a one-chip microcomputer capable of performing such processing is an 8-bit microcomputer "Z86C04" manufactured by Zilog.

In such a structure, when an incoming call is received,
The microcomputer 34 is interrupted by the ringer signal in the period T1, the processing of the CPU 41 starts from step 101 of the routine 100, then initialization is performed in step 102, and subsequently, in step 103, the main of the signal SCI is executed. Time waiting is performed until the time reaches the beginning of the data (the start of word W1).

Then, when the time comes to the head of the main data of the signal SCI, the process proceeds to step 111, in which the head start bit in each word is received, and then in step 112,
8-bit data of the main body following the start bit is received and written in the RAM 43, and then step 113
At, the last stop bit of each word is received. In this case, in steps 111 to 113, whether the bit is “0” or “1” can be known from the time measured by the timer 46.

Then, the process proceeds from step 113 to step 114, and in step 144,
It is checked whether or not the data of "the number of words indicated by the second word W2 + 1" is received, that is, whether or not the data up to the word of the last checksum is received is checked. Returns from step 114 to step 111. Thus, in steps 111 to 114, all the words of the main data are received, and the net data (8-bit data) in each word is written in the RAM 43.

Then, the processing advances from step 114 to step 121. In this step 121, processing such as data check is performed using the checksum written last, and then in step 122, the microcomputer 20 In response, for example, by interruption, the reception of data by the cola ID signal SCI is notified, and the routine 100 is ended in step 123.

On the other hand, in the microcomputer 20, when an incoming call is received, the detection circuit 24 notifies the incoming call, so that the incoming call is processed. Then, there is a cola ID signal SCI from the microcomputer 34.
When it is notified that the data is present, the microcomputer 34 requests the microcomputer 34 to transmit the data at an appropriate time, and receives the data from the microcomputer 34 by serial communication, for example. Then, the received data is processed for display and then supplied to the LCD 27 through the drive circuit 26, and the telephone number of the other party is displayed on the LCD 27.

Thus, in this telephone, the telephone number of the other party sent by the cola ID signal SCI can be displayed on the LCD 27. In this case, the demodulation of the cola ID signal SCI is performed by the one-chip microcomputer. Since it is performed by 34, the cost is lower than that when a dedicated demodulation IC is used.

Further, the microcomputer 34 is an RA
Since the RAM 43 has the M43 and holds the data demodulated from the cola ID signal SCI in the RAM 43, the main microcomputer 20 may receive the data in the RAM 43 and perform the display process at any time. Therefore, the software design is simplified.

FIG. 4 shows an example of measuring the characteristics of the demodulation circuit 30 described above. That is, the telephone line 1 is 1 km
The pseudo line is configured to show an equivalent reactance of 270 Ω + 50 nF per. Then, the horizontal axis of FIG. 4 shows the length of the pseudo line, and the vertical axis shows the average signal level of the received cola ID signal SCI and the number of times the signal SCI was successfully demodulated. The number of experiments is 20 for each line length.
Times.

According to the standards of each country, even if the margin of 5 dB is observed, it is sufficient that the signal level normally operates up to -30 dBm. However, according to the above experimental results, the reception of -30 dBm is possible. The operation at the level has been cleared. Also, 95% demodulation was successful even at a reception level of -33.6 dBm. Therefore, the demodulation circuit 30 described above has sufficient characteristics.

[0033]

According to the present invention, the cost is lower than the case of using a dedicated demodulation IC. Also, the software design in the main microcomputer is simplified.

[Brief description of drawings]

FIG. 1 is a connection diagram illustrating one embodiment of the present invention.

FIG. 2 is a system diagram showing a part of one embodiment of the present invention.

FIG. 3 is a flowchart showing an embodiment of the present invention.

FIG. 4 is a diagram showing a measurement example of characteristics of one embodiment of the present invention.

FIG. 5 is a diagram showing a signal format.

[Explanation of symbols]

 1 telephone line 12 interface circuit 13 speech network circuit 14 transmitter 15 receiver 20 microcomputer (for main) 21 operation key 24 detection circuit 25 ringer 26 drive circuit 27 LCD 30 demodulation circuit 31 high-pass filter 32 low-pass filter 33 waveform shaping circuit 34 Microcomputer (for demodulation)

Claims (2)

[Claims] 1. A demodulation circuit for demodulating the binary data from an FSK signal which is sent to a gap of a ringer signal at the time of an incoming call and is FSK-modulated by binary data indicating a telephone number or the like. It has a waveform shaping circuit for shaping the FSK signal into a rectangular wave signal, and a 1-chip microcomputer to which the rectangular wave signal is supplied. The 1-chip microcomputer measures the time length of each cycle of the rectangular wave signal. By doing so, the value of the binary data is discriminated, the discrimination result is held in the RAM, and the held discrimination result is transferred to the main microcomputer in response to a request from the main microcomputer. ID signal demodulation circuit. 2. A demodulator circuit for a cola ID signal according to claim 1, wherein the FSK signal is supplied to the waveform shaping circuit through a low pass filter and a high pass filter.