JPH03192840A - Synchronization/asynchronization conversion integrated circuit - Google Patents

Abstract

PURPOSE:To realize space saving of a printed circuit board with a synchronization/ asynchronization conversion integrated circuit mounted thereon by incorporating a selective circuit (selector) selecting a synchronous signal and an asynchronous signal with a control section to eliminate the need for an externally mounted selective circuit for the synchronous signal and the asynchronous signal. CONSTITUTION:A synchronization/asynchronization conversion circuit 20 consists of a transmission section 21 and a reception section 22. In the case of asynchronous data transmission between a personal computer and a MODEM, a control signal 70 allows the signal output of a selector 30 and the signal input of a selector to be thrown to the position of the transmission section 21 and allows the signal output of a selector 50 and the signal input of a selector 60 to be thrown to the position of the reception section 22. The asynchronous signal inputted from the personal computer is converted into a synchronous signal and the synchronous data from the opposite party demodulated at a MODEM integrated circuit section is converted into an asynchronous signal. In the case of synchronous data transmission between the personal computer and the MODEM, the control signal 70 allows the signal output of the selector 30 to be thrown to the position of the selector 40 and the signal input of the selector 40 to be thrown to the position of the selector 30. Moreover, the signal output of the selector 50 is thrown to the position of the selector 60 and the signal input of the selector 60 is thrown to the position of the selector 50.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a synchronous-to-asynchronous conversion integrated circuit for a modem (hereinafter referred to as a modem) in a data transmission system.

BACKGROUND OF THE INVENTION In recent years, data transmission using telephone lines has been developing. In particular, PC communications for exchanging data between personal computers (hereinafter referred to as personal computers) are popular in the United States and Japan. A modem converts a digital signal from a computer into an analog signal on a telephone line. Modems must comply with internationally established standards (this is called the CCI TT standard). Conventionally, asynchronous data transmission between modems and personal computers has been the mainstream. However, as data transmission speeds continue to increase, the modem modulation and demodulation method used to be frequency modulation (FSK), but recently phase modulation (PSK) and amplitude phase modulation (QAM) have been adopted. It's coming. PSK and QAM
The method is a synchronous data transmission method that requires modulation timing.

Therefore, the modem must convert asynchronous data from the personal computer into synchronous data and send it over the telephone line. Furthermore, synchronous data on the telephone line must be converted into asynchronous data and transmitted to the personal computer. A synchronous-asynchronous conversion circuit converts this synchronous data and asynchronous data. This conversion method is based on CCITT V, 22, which is the standard for 12008PS full-duplex modem, or CCITTV, which is the standard for 2400BPS full-duplex modem.
It is defined in Tv, 22biS. This circuit is currently available as an integrated circuit.

A modem using a conventional synchronous-asynchronous conversion integrated circuit will be described below.

FIG. 2 is a block diagram of a modem using a conventional synchronous-asynchronous conversion integrated circuit. It has a function of converting (referred to as demodulating) an analog signal sent from the other party through the telephone line 3 into a digital signal to the personal computer 1 (referred to as demodulation). Modem 2 is R for connecting to PC 1.
It is composed of a 3-232C interface circuit 4, a synchronous/asynchronous conversion integrated circuit 5, a modulation/demodulation integrated circuit 6, and a telephone line connection circuit 7.

Data transmission using the modem configured in this way will be explained.

Signals from the personal computer 1 are input to the synchronous/asynchronous conversion integrated circuit 5 through the R3-232C interface circuit 4, convert the asynchronous data to synchronous data, and are modulated into analog signals by the modulation/demodulation integrated circuit 6. Furthermore, it is sent to the telephone line 3 through the telephone line connection circuit 7. On the other hand, a signal sent from the other party through the telephone line 3 is inputted from the telephone line connection circuit 7 to the modulation/demodulation integrated circuit 6 and demodulated into a synchronous digital signal. This signal is converted into asynchronous data by the synchronous-asynchronous conversion integrated circuit 5, and R3-2
The data is transmitted to the personal computer 1 through the 32C interface circuit 4.

Problems to be Solved by the Invention Conventionally, asynchronous data transmission between the personal computer 1 and the modem 2 has been the mainstream, but recently synchronous data transmission has also come into widespread use. In this case, it is necessary to directly connect the R3-232C interface circuit and the modulation/demodulation integrated circuit without passing through the synchronous/asynchronous conversion integrated circuit.

Therefore, the conventional synchronous-asynchronous conversion integrated circuit has the problem that a circuit for switching between synchronous signals and asynchronous signals must be added to the input/output section.

The present invention solves the above-mentioned conventional problems, and aims to provide a synchronous-asynchronous conversion integrated circuit that can select between a synchronous signal and an asynchronous signal using a control signal.

Means for Solving the Problems To achieve this object, the synchronous-asynchronous conversion integrated circuit of the present invention has a configuration that includes a selection circuit (hereinafter referred to as a selector) that selects between a synchronous signal and an asynchronous signal using a control signal. have.

Effect: This configuration eliminates the need for a circuit for selecting between synchronous and asynchronous signals as an external additional circuit, making it possible to save space on the printed circuit board on which the synchronous-asynchronous conversion integrated circuit is mounted.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a synchronous-asynchronous conversion integrated circuit according to an embodiment of the present invention.

The synchronous asynchronous conversion integrated circuit 10 is a synchronous asynchronous conversion circuit 2.
0. Selectors 30, 40, 50. ．． The selectors 30 to 60 are controlled by a control signal 70. Further, the synchronous/asynchronous conversion circuit 20 includes a transmitting section 21 and a receiving section 22.

The operation of the synchronous-asynchronous conversion integrated circuit configured as described above will be explained below. First, in the case of asynchronous data transmission between the personal computer and the modem, the control signal 70 causes the signal output of the selector 30 to be placed on the transmitting section 21 side, and the signal input of the selector 40 is similarly placed on the transmitting section 21 side. Further, the signal output of the selector 50 is made to the receiving section 22 side, and the signal input of the selector 60 is also made to the receiving section 22 side. The asynchronous type transmission signal inputted from the personal computer is inputted by the selector 30 to the transmission section 21 of the synchronous/asynchronous conversion circuit 20, and the CCI T
The asynchronous signal is converted into a synchronous signal by the method defined in the T standard (V, 22, V, 22bis). This is then sent through selector 40 to the modulation/demodulation integrated circuit. On the other hand, the synchronous data from the other party demodulated by the modulation/demodulation integrated circuit section is inputted to the reception section 22 of the synchronous/asynchronous conversion circuit 20 by the selector 50, and is sent using a constant molar delay method according to the CCITT standard (V, 22, V, 22bis). Converts a synchronous signal to an asynchronous signal. This is then sent through the selector 60 to the computer.

Next, in the case of synchronous data transmission between the personal computer and the modem, the control signal 70 sets the signal output of the selector 30 on the selector 40 side, and sets the signal input of the selector 40 on the selector 30 side. Further, the signal output of the selector 50 is set to the selector 60 side, and the signal input of the selector 60 is set to the selector 50 side. The received signal from the modulation/demodulation integrated circuit is a synchronous type signal, and is sent from the selector 50 to the selector 60 as it is to the computer.

Effects of the Invention As described above, according to this embodiment, since the selector for synchronous and asynchronous signals is built-in, data transmission between the computer and the modem can be performed regardless of whether the data transmission is synchronous or not by switching the control signal. It is possible to provide a synchronous-to-asynchronous conversion integrated circuit that handles both types of signals, even if they are of the asynchronous type. Furthermore, the space required for the printed circuit board on which the modem's modulation/demodulation integrated circuit and synchronous/asynchronous conversion integrated circuit are mounted can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a synchronous asynchronous conversion integrated circuit according to the present invention, and FIG. 2 is a block diagram of a modem including a conventional synchronous asynchronous conversion integrated circuit. 1...PC, 2...Modem, 3.
... Telephone line, 4 ... R8-232G interface circuit, 5 ... Synchronous asynchronous conversion integrated circuit, 6 ... Modulation and demodulation integrated circuit, 7 ... ...
・Telephone line connection circuit, 10...Synchronous asynchronous conversion integrated circuit, 20...Synchronous asynchronous conversion circuit, 30
,40,50.60...Selector,70...
···Control signal.

Claims (1)

[Claims] a synchronous-asynchronous conversion circuit; a first selection circuit that selects whether or not to input a transmission/reception input signal to the synchronous-asynchronous conversion circuit section according to a synchronous-asynchronous selection control signal; A synchronous/asynchronous conversion integrated circuit comprising: a second selection circuit that selects a signal and a signal of the first selection circuit.