JPH06152662A - Data modem - Google Patents

Abstract

PURPOSE:To obtain a data MODEM in which MODEM of different modulation systems is realized by the same equipment. CONSTITUTION:The MODEM is provided with a DSP(digital signal processor) 1 provided with a built-in instruction ROM 5, an external RAM 6 connecting to an external instruction area of the DSP 1, an external ROM 7 storing plural kinds of a program executed by the DSP 1, and a transfer circuit 8 to transfer the content of the external ROM 7 to the external RAM 6 by a command of the DSP 1. The transfer circuit 8 is started by the program written in the built-in instruction ROM 5 of the DSP 1 and the program of the external ROM 7 is transferred to the external RAM 6. The DSP 1 implements the signal processing required for the data MODEM with the program written respectively to the built-in instruction ROM 5 and the external RAM 6.

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 the structure of a digital signal processor (DSP) and its peripheral circuits.

[0002]

2. Description of the Related Art In the past, advances in DSPs in data modems have expanded the scale of digital signal processing that can be processed. As a result, the communication speed of the data modem that can be realized by the DSP has been dramatically improved. However, the increase in communication speed increases the types of modulation / demodulation methods that must be realized, and at the same time, the cycle of product change is shortened, which causes disadvantages for manufacturers and consumers.

FIG. 3 is a diagram showing a recommendation of a data modem using a telephone network which is currently recommended by CCITT (International Telegraph and Telephone Inquiry Committee). As shown in FIG.
As the modulation method in this recommendation, FSK is frequency modulation, PSK is phase modulation, QAM is quadrature amplitude modulation, and TCM is TCM.
Represents trellis code modulation, and EC represents an echo canceller system.

Such diversification of the modulation / demodulation system is required to mount as many modem recommendations as the data modem should have on one device, and as a result, the scale of the data modem is increased.

FIG. 4 is a block diagram of a conventional data modem. As shown in FIG. 4, the conventional data modem includes a DSP 1a having a built-in instruction ROM 5 and the DSP 1a.
An analog front edge (AFE) 2 which is connected to 1a and converts an analog signal on the line into a digital signal, and a DS
A PLL circuit 3 connected to the P1a and the AFE2 to generate a clock for transmission and reception, and a data terminal device (DT).
E) 9 and a host processor 4 that controls the interface with the DTE 9 and the entire modem.

In such a data modem, at the time of transmission, first, the transmission data transmitted from the DTE 9 is loaded into the host processor 4. This transmission data is defined and converted by a protocol (communication procedure), and is converted to DS as modulation data.
Sent to P1a. The DSP 1a modulates the modulation data received from the host processor 4 by a programmed modulation method and converts it into a telephone network band signal. The converted signal is converted into an analog signal by the AFE 2 and then transmitted to the public network.

Next, at the time of reception, the analog signal received from the public line network is converted into a digital signal by AFE2 and sent to the DSP 1a. The DSP 1a demodulates the received signal by the programmed demodulation method and extracts the demodulated data. The demodulated data demodulated by the DSP 1a is sent to the host processor 4 and converted into received data according to a predetermined protocol. In addition, the host processor 4
The received data output from is received by the DTE 9.

Here, the PLL circuit 3 reproduces the transmission timing and the reception timing, and supplies the operation timing clock to the DSP 1a, the AFE 2 and the host processor 4.

However, the DSP 1a has a built-in instruction ROM.
Based on the program stored in 5, the data modem is operated for modulation and demodulation. The operation of this modulation / demodulation differs depending on the modem recommendation specified by the recommendation. For example, V.
21 is an FSK modulation / demodulation method, V.V. 22 is a PSK modulation / demodulation system, V.V. 29 is a QAM modulation / demodulation system, V.V. 32 is a TCM modulation / demodulation system with an echo canceller. Also, the same P
V. 22 and V.I. 26, V.I. In No. 27, the same program cannot be used because the modulation speed and the modulation frequency are different. The same applies to FSK, QAM
It can be said to the method. Therefore, separate programs are required for the modem recommendations specified in the recommendations. Further, since the instruction memory of the DSP 1a is a ROM and cannot be rewritten, once the device is configured as a data modem, it cannot be changed to another modem recommended by the modem.

[0010]

In the conventional data modem described above, the number of program steps that can be executed is determined by the capacity of the DSP's built-in instruction ROM. Therefore, the modulation / demodulation methods of many types of data modems are the same. The drawback is that it is difficult to achieve above. Also,
With regard to the new modulation / demodulation method, the configuration of the data modem has to be changed anew, so that there is a drawback that the data modem must be redesigned every time a new recommendation appears, and the consumer side It has the disadvantage of having to purchase a new data modem each time.

An object of the present invention is to provide a data modem capable of realizing modems of different modulation systems on the same device and adapting to various changes.

[0012]

The data modem of the present invention comprises a digital signal processor having a built-in instruction ROM, an external RAM connected to an external instruction area of the digital signal processor, and the digital signal processor. An external ROM storing a plurality of types of programs to be executed by the signal processor; and an instruction transfer circuit for transferring the contents of the external ROM to the external RAM in response to a command from the digital signal processor,
The instruction transfer circuit is activated by the program written in the built-in instruction ROM of the digital signal processor to transfer the program stored in the designated area of the external ROM to the designated area of the external RAM. The digital signal processor is configured to perform necessary signal processing by a program written in the built-in instruction ROM and a program written in the external instruction RAM.

[0013]

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

FIG. 1 is a block diagram of a data modem showing a first embodiment of the present invention. As shown in FIG. 1, this embodiment has a DSP 1 having a built-in instruction ROM 5, an analog front end (AFE) 2 for converting an analog signal on a line into a digital signal, and a PLL for generating a transmission clock and a reception clock. Circuit 3 and data terminal equipment (DTE) 9
A host processor 4 for interfacing with the DTE 9 and controlling the entire modem, an external RAM 6 mapped in the external instruction area of the DSP 1, an external ROM 7 connected to the external RAM 6, and an external R
It has an instruction transfer circuit 8 for transferring the contents of the OM 7 to the external RAM 6. Of these, the internal instruction ROM 5 is DS
Part of the instructions of P1 are stored, and the external ROM 7 stores a modem modulation / demodulation program for the DSP1. Further, the transfer circuit 8 transfers the contents of the designated area of the external ROM to the external RAM 6 according to a command from the DSP 1.

In such a data modem, first, the DSP
External ROM for modem modulation / demodulation program
7 to the external RAM 6. The program for this transfer is stored in the internal instruction ROM 5 of the DSP 1. That is, the DSP 1 executes a program written in the built-in instruction ROM 5 to set a predetermined address of the external ROM 7 in the transfer circuit 8, and then issues a transfer instruction to the transfer circuit 8. The transfer circuit 8 receiving the instruction from the DSP 1 transfers the contents of the external ROM 7 to the external RAM 6 only for the designated area. When the program has been transferred from the external ROM 7 to the external RAM 6, the program area used by the DSP 1 is changed from the internal instruction ROM 5 to the external RAM 6, and the DSP 1 operates according to the program written in the external RAM 6. Of course, the addresses of the internal instruction ROM 5 and the external RAM 6 may be consecutive, and the internal instruction ROM 5 and the external RAM 6 may be consecutive.
A modem modulation / demodulation program may be written in both of the above.

Next, an outline of the operation of the data modem will be described. At the time of transmission, the transmission data transmitted from the DTE 9 is fetched by the host processor 4, the transmission data is converted by a predetermined protocol (communication procedure), and the modulated data is transmitted to the DSP 1. At this time, the DSP 1 modulates the modulated data by the programmed modulation method and converts it into a telephone network band signal. The converted signal is A
The FE2 converts the digital signal into an analog signal and transmits it to the public line network.

On the other hand, at the time of reception, the analog signal received from the public line network is converted into a digital signal by the AFE2 and sent to the DSP1. The DSP 1 demodulates the received signal by the programmed demodulation method and extracts the demodulated data. The demodulated data demodulated by the DSP 1 is sent to the host processor 4 and converted into received data according to a predetermined protocol. Further, the received data output by the host processor 4 is received by the DTE 9.
The PLL circuit 3 reproduces the transmission timing and the reception timing, and the DSP 1, AFE 2, and host processor 4
To the operation timing clock.

FIG. 2 is a block diagram of a data modem showing a second embodiment of the present invention. As shown in FIG. 2, in this embodiment, the built-in instruction ROM 5 of the DSP 1 in the first embodiment of FIG. 1 described above is arranged as an external instruction ROM 10 in the external instruction space, and otherwise it is exactly the same. Therefore, the description is omitted. In this way, by displacing all the storage means of the program executed by the DSP 1 out of the DSP 1, the DSP 1 itself can be simplified.

In short, in the present embodiment, the modem modulation / demodulation program executed by the DSP 1 is stored in the external ROM 7 and transferred again to the external RAM 6 for each type of modem, so that many types of modem modulation / demodulation systems can be used. It can be realized with the same system configuration. Also, external R
The configuration of the OM 7 and the external RAM 6 has the advantage that the processing speed of the DSP 1 does not have to be reduced by using a large-capacity mask ROM or PROM as the external ROM and using a high-speed RAM.

[0020]

As described above, the data modem of the present invention can support various modem systems by transferring the DSP program to the external RAM in accordance with the modem modulation / demodulation system, and further, the DSP can be used. There is an effect that the limited instruction space of can be effectively used. Further, in the present invention, since the modem system can be easily changed by changing (replacement) the external ROM, it is easy to upgrade the version due to the appearance of a new modem recommendation, and it is not necessary to change the configuration itself of the data modem. is there.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a data modem showing a second embodiment of the present invention.

FIG. 3 is a diagram showing the contents of recommendation of a data modem recommended by CCITT.

FIG. 4 is a block diagram of a data modem showing a conventional example.

[Explanation of symbols]

 1 Digital Signal Processor (DSP) 2 Analog Front End (AFE) 3 PLL Circuit 4 Host Processor 5 DSP Built-in Instruction ROM 6 External RAM 7 External ROM 8 Transfer Circuit 9 Data Terminal Device 10 External Instruction ROM

Claims (2)

[Claims] 1. A digital signal processor having a built-in instruction ROM, an external RAM connected to an external instruction area of the digital signal processor, and a plurality of types of programs executed by the digital signal processor. The stored external ROM and the external ROM according to a command from the digital signal processor
An instruction transfer circuit for transferring the contents of the above to the external RAM, and the instruction transfer circuit is activated by a program written in the built-in instruction ROM of the digital signal processor to specify the external ROM. A program stored in a specified area of the external RAM, and the digital signal processor causes the signals written by the program written in the built-in instruction ROM and the program written in the external instruction RAM. A data modem characterized by performing processing. 2. A digital signal processor,
An external instruction ROM connected to the external instruction area of the digital signal processor, an external ROM storing a plurality of types of programs executed by the digital signal processor, and an external RAM connected to the external instruction ROM An instruction transfer circuit for transferring the contents of the external ROM to the external RAM in response to a command from the digital signal processor, and the external instruction R
The program written in the OM activates the instruction transfer circuit to transfer the program stored in the designated area of the external ROM to the designated area of the external RAM, and the digital signal processor is connected to the external unit. A data modem characterized by performing necessary signal processing by a program written in an instruction ROM.