JPH06164655A - Data modem - Google Patents

Abstract

PURPOSE:To deal with various modem systems with one device by providing a RAM, ROM and transfer circuit for transferring one of modulation/ demodulation programs stored in an external ROM to the RAM at a digital signal processor (DSP.) CONSTITUTION:First of all, the modulation/demodulation program of a MODEM to be executed at a DSP 16 is transferred from an external ROM 17 to an internal instruction RAM 62. Because of this transfer, the program is stored in an internal instruction ROM 61, and the DSP 16 executes the program written in the ROM 61, sets the previously decided address of the ROM 17 to a transfer circuit 63 and continuously issues the instruction of transfer. The circuit 63 transfers only the contents in the designated area of the ROM 17 to the RAM 62. When the program is completely transferred to the RAM 62, the program area used for the DSP 16 is changed from the instruction ROM 61 to the RAM 62, and the DSP 16 is operated corresponding to the program written in the RAM 62.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data modem, and more particularly to a data modem for transmitting digital data via a telephone line.

[0002]

2. Description of the Related Art Recent advances in DSP have expanded the scale of digital signal processing that can be processed. As a result, DSP
The communication speed of the data modem that can be realized by has dramatically improved. However, the improvement in communication speed will increase the types of modulation / demodulation methods that must be realized, and on the other hand, the cycle of product modem change will be shortened.
Disadvantages have arisen for both manufacturers and consumers. Table 1 presently CCITT (International Telegraph and Telephone Inquiry Committee)
The following are recommendations for data modems that use the telephone network recommended by.

[0003]

[Table 1]

The diversification of the modulation / demodulation system as described above has forced the data modem to mount as many modem recommendations as possible to be realized on one device, and as a result, the scale of the data modem has become large.

As shown in FIG. 2, a conventional data modem includes a digital signal processing device (hereinafter referred to as DSP) 11 having a built-in instruction ROM and an analog front end (hereinafter referred to as AFE) for converting an analog signal on a line into a digital signal.
12, a PLL circuit 13 for generating a clock for transmission and reception, an interface with a DTE (data terminal device) 15, and a host processor 14 for controlling the entire modem
It consisted of and.

Next, the operation of the conventional data modem will be described.

On the transmission side, the transmission data transmitted from the DTE 15 is taken in by the host processor 14, the transmission data is converted by a predetermined protocol (communication procedure), and the modulated data is transmitted to the DSP 11. DSP1
In 1, the modulation data is modulated by the programmed modulation method and converted into a telephone network band signal. The converted signal is converted by the AFE 12 from a digital signal to an analog signal and transmitted to the public line network. On the receiving side, the analog signal received from the public circuit network is converted into a digital signal by the AFE 12 and sent to the DSP 11. D
At SP11, the received signal is demodulated by the programmed demodulation method and demodulated data is extracted. The demodulated data demodulated by the DSP 11 is sent to the host processor 14,
It is converted into received data according to a defined protocol. The received data output by the host processor 14 is DT
Received by E15. The PLL circuit 13 reproduces the transmission timing and the reception timing to reproduce the DSP 11 and AFE.
12. A clock is supplied to the host processor 14 as an operation timing clock.

The DSP 11 performs a modulation / demodulation operation of the data modem according to a program stored in a built-in instruction ROM. The calculation of modulation / demodulation depends on the plan of the above-mentioned CCITT modem recommendation. For example, as shown in Table 1, the recommendation V. 21 is an FSK modulation / demodulation system, which is recommended in the above V. 22 is a PSK modulation / demodulation system, which is recommended in the above V. 29 is QA
M modulation / demodulation method, above-mentioned Recommendation V. 32 is a TCM modulation / demodulation system with an echo canceller. Further, even if the same PSK method is used, the recommendation V. 22 and V.I. 26 and V.I. No. 27 cannot use the same program because the modulation speed and the modulation frequency are different. The same applies to FSK and QA
The same applies to the M method. Therefore, a separate program is required for each recommendation of the applied modem. Further, since the instruction memory of the DSP 11 is generally a ROM and cannot be rewritten, once the device is configured as a data modem, it cannot be changed to another modem recommended by another modem.

[0009]

Since the conventional data modem described above uses the ROM as the instruction memory of the DSP, it is impossible to rewrite the program into different kinds of programs required for each CCITT recommendation to be applied. However, there is a drawback in that a new data modem is redesigned each time the new recommendation is introduced, and the user needs to purchase a new data modem each time.

[0010]

A data modem of the present invention is a data modem equipped with a digital signal processing device for controlling transmission / reception modulation / demodulation by a data modulation / demodulation program, and stores a first program which is the data modulation / demodulation program. External read only memory (RO
Random access memory (RA) in which the digital signal processing device stores the first program.
M), a ROM that stores a second program, and a transfer circuit that transfers the first program stored in the external ROM by the second program to the RAM.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a data modem of the present invention.

The data modem of this embodiment, as shown in FIG. 1, has an AFE 12 and P which are the same components as those of the conventional example.
In addition to the LL 13, the host processor 14, and the DTE 15, an internal instruction ROM 61, an internal instruction RAM 62, and an external RO that store some of the instructions instead of the conventional DSP 11.
The DSP 16 having a transfer circuit 63 for transferring the contents of M17 to the RAM 62 and the D16 connected to the internal instruction RAM 62
An external ROM 17 storing a plurality of modulation / demodulation programs for the SP 16 is provided.

Next, the operation of this embodiment will be described.

First, a modem modulation / demodulation program executed by the DSP 16 is transferred from the external ROM 17 to the internal instruction RAM 6
Transfer to 2. The program for this transfer is stored in the internal instruction ROM 61, and the DSP 16 first executes the program written in the internal instruction ROM 61 to set a predetermined address of the external ROM 17 in the transfer circuit 63, Then, a transfer command is issued. The transfer circuit 63 has an external ROM 1 only in a designated area.
7 is transferred to the internal instruction RAM 62. Internal command R
When the program has been transferred to the AM 62, the program area used by the DSP 16 is changed from the internal instruction ROM 61 to the internal instruction RAM 62, and the DSP 16 operates according to the program written in the internal instruction RAM 62. Of course, since the addresses of the internal instruction ROM 61 and the internal instruction RAM 62 may be consecutive, the modem modulation / demodulation program may be written in both the internal instruction ROM 61 and the internal instruction RAM 62. The operation as a data modem is the same as that of the conventional example, and therefore its description is omitted.

As described above, according to the present invention, the modem modulation / demodulation program executed by the DSP is stored in the external ROM and is transferred again to the internal instruction RAM for each type of modem, so that various types of modem modulation / demodulation systems can be used. On the other hand, they can be realized with the same system configuration. Further, in the configuration of the external ROM and the internal instruction RAM, a large capacity mask ROM or PROM can be used as the external ROM, and the internal instruction RAM can be accessed at high speed, so that the processing speed of the DSP is not reduced. It also has the advantage of being completed.

[0017]

As described above, the data modem of the present invention is an external ROM storing a plurality of modulation / demodulation programs.
Since the DSP includes a RAM, a ROM, and a transfer circuit that transfers one of the modulation / demodulation programs stored in the external ROM to the RAM, one device can support various modem systems. There is an effect that. Further, since the modem system can be easily changed by changing the external ROM, it is possible to easily upgrade the version of each new CCITT recommendation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a data modem of the present invention.

FIG. 2 is a block diagram showing an example of a conventional data modem.

[Explanation of symbols]

 11, 16 DSP 12 ATE 13 PLL 14 Host processor 15 DTE 17 External ROM 61 Internal ROM 62 Internal RAM 63 Transfer circuit

Claims (2)

[Claims] 1. A data modem comprising a digital signal processing device for controlling transmission / reception modulation / demodulation by a data modulation / demodulation program, comprising an external read only memory (ROM) storing a first program which is the data modulation / demodulation program, A digital signal processing device stores a random access memory (RAM) for storing the first program, a ROM for storing the second program, and a first program stored in the external ROM by the second program. A data modem comprising: a transfer circuit for transferring to the RAM. 2. The data modem according to claim 1, wherein the RAM stores all programs necessary for controlling the modulation / demodulation of the digital signal processing device.