CS231021B1 - Connection for incoming data signal treatment in modems and treatment of signal identifying carrier frequency - Google Patents

Abstract

The purpose of the invention is to remove undesirable at the end of transmission in asynchronous Modem Transfer Mode and Filter Out startbits of insufficient width. Listed effect is achieved by a confusion in the receiver modem, consisting of inserting a circuit connected so that the output from the receiver demodulator it is connected to the auxiliary sliding input a register controlled by a precision generator of variable frequency pulses according to the selected transmission speed. Information delay time it is changeable in the shift register length of the information byte and by the length of the delay carrier identification signal disappears frequency to demodulated information. Additional logic circuits also provide filtering insufficient width of startbit e carrier frequency signal correction. This modified signal then controls the output shift register information to output Modem Amplifiers, which is desirable changing the relative position of information and identification signal and thus unblock the fault at the end of the broadcast.

Description

(54) Connection for modifying the received data signal in the modem and modifying the carrier frequency identification signal

The purpose of the invention is to eliminate unwanted disturbances at the end of transmission in an asynchronous mode of transmission of information by means of a modem and to filter out startbits of insufficient width. This effect is achieved by modifying the receiver of the modem by inserting a circuit connected so that the output from the receiver demodulator is connected to the input of an additional shift register controlled by a precise variable frequency pulse generator according to the selected transfer rate. The delay time of the information in the shift register is variable according to the length of the information byte and according to the delay time of the carrier frequency identification signal to the demodulated information. The additional logic circuitry also filters out the startbit bits of insufficient width e of the carrier identification signal. This modified signal then controls the output of the shift register information to the output amplifiers of the modem, thereby desirable to change the relative position of the information and identification signal and thereby to unblock the fault at the end of the transmission.

23,02,

The invention relates to a remote data transmission device, referred to as a modem, in which information is transmitted over a link in the form of a frequency modulated signal.

Modems can transmit information in different modes of operation. In terms of ways of connecting a pair of remote modems can be generally divided remote transmission systems into two and four wires depending on where the connection is made by one or two pairs of connecting wires. systems advantageous use of two-wire system. In this case, the information is transmitted alternately back and forth over the same pair of wires in the so-called asynchronous mode. Each byte of information is provided with additional bits to indicate the start and end of the byte, and the number of stop bits can be extended to two. Modems are generally designed so that if they do not transmit themselves, they are automatically switched to receive. The transmitting modem always starts transmitting by switching on the carrier frequency, whose presence on the line is detected by the detection circuit on the receiving side, which opens the data decipherers and paves the way for receiving the information. With the appropriate time delay after the carrier frequency is switched on, the transmitting modem then transmits the message and switches off the carrier. The receiving modem demodulates the message and transmits it to the appropriate information processing device in a modified digital form. Together with the information demodulation, the receiving modem sends to the information processing device a carrier frequency identification signal generated by the receiver detection circuit. The detection circuit shows both the required amplitude hysteresis and the time-delay of the carrier frequency identification signal.

When changing the direction of transmission, or breaks in transmission, the carrier frequency is switched on and off at which undefined transients occur on the line, which even the most sophisticated filters and demodulators are unable to eliminate. As a rule, the faults when the carrier is switched on are unblocked by the modem receiver logic by delaying the start of the carrier frequency identification signal so that the path for receiving information is closed at the moment of the fault. The problem arises at the end of transmission when the carrier frequency disappears. The receiver detection circuit responds to the carrier termination with a delay, so that the fault is demodulated and then transmitted to the information processing device. This causes the message to be degraded, output devices such as printers, display terminals, etc., add extra nonsensical characters after the message, and transmission errors are indicated.

This problem is taught by software inserting marks for the beginning and end of the message in the text. This solution suits the operating unit side, not the age generally on the peripheral side. Repair requires various working changes of software and hardware character.

The above-mentioned shortcomings in asynchronous transmission are overcome by the circuitry of the invention, which consists in storing the received information after demodulation in an additional shift register which is controlled by a precise pulse generator, the length of the register being variable according to the carrier frequency identification signal relative to the received information. The circuit according to the invention further comprises a circuit enabling recognition of insufficient width startbit and a circuit for modifying the carrier frequency identification signal that controlled the output of the shift register information to the modem output amplifiers, thereby desirable changing the relative position of the information and identification signal and thereby unblocking the fault broadcasting. The circuit according to the invention is built into its own modem, utilizing its internal clock pulses, so that its own synchronization is automatically overfilled when the transfer rates are switched.

The circuit according to the invention is connected so that the output from the modem receiver demodulator is connected to the input of a valid startbit detection circuit, the output of which is connected to the input of the byte processing controller. The controller output is connected to the gating input of the bit counter and to the reset inputs of the valid start-up detection circuit, the carrier identification signal conditioning circuit, and the synchronization pulse generator. The output from the carrier frequency detection circuit of the modem itself is connected to the second input of the carrier identification signal processing circuit, while the output of the carrier identification signal processing circuit is connected to the second shift register input. Furthermore, this output is connected to the modem logic and a modified carrier frequency identification signal is passed through it. The clock input of the synchronized pulse generator is outputted from the crystal controlled modem logic oscillator, while the output of the generator is connected to the clock inputs of the shift register and the bit counter. The shift register output is connected to the modem logic and transmitted information is transmitted over it.

In this way, it is possible to filter out the failure start-bits during transmission and to accurately shatter the serial information in the modem, but first of all to eliminate unwanted disturbances when the carrier frequency is switched off.

The drawing schematically shows one possible circuit connection according to the invention. By input 301, a signal from the carrier frequency detection circuit of the modem is received to the carrier 2 signal conditioning circuit 2. The signal rise at the output 302 coincides with the signal rise at the input 301 and the signal remains set for the entire time of transmission, the signal from output 302 leads to the reset input of shift register 6 and is connected to the logic of the modem. carrier frequency identification. The second gate of the circuit 2 is connected to an output 301 from a modem demodulator, followed by a series-ordered data information. No third gate input is connected to the output 401 of the byte processing controller 6. Upon the arrival of a valid start bit with the signal at input 201, the byte controller 6 triggers the byte controller which, at its output 401, unlocks the pulse generator 1 and the 3-bit counter. At the same time, the signal at output 401 blocks the indication of a new valid startbit during the start of byte processing. The synchronization pulse generator 1 generates from the base clock signal supplied from the crystal-controlled modem logic oscillator through input 101 synchronization pulses at output 102. These synchronization pulses are used as shifting pulses at the shift register input 6 where it controls the feed and output data information, on the read-in input of the counter. 3 bits, whose variable preset allows setting any counter capacity in the range of 1 to 15 bits / byte. Once the last byte bit is processed, the byte processing controller is reset and the cycle repeats with the arrival of a valid startbit of the next byte. All bytes of the message are transmitted in the same way. When the last byte of the message is being fed into shift register 6, the penultimate byte is output by output 602 to the modem logic. Thereafter, the circuit waits for a fault signal to be received by the input 60 '. or on signal termination Carrier frequency identification at input 301 _t . thereby triggering a fault or empty byte entry into the shift register 6 and transmitting the previous register content - the last byte of the message - to the logic of the modem by output 602. The total delay of shift register 6 and the counter of 3 bits are selected to transmit the last byte and then, after it has been fully transmitted, the carrier frequency modification circuit J terminates the duration of the signal at output 302. After this output, the carrier frequency identification signal goes into the modem logic. At the same time, the shift register 3i resets so that the fault byte is cleared. . '

The invention can be applied to all minor variation modem devices according to the particular design of the respective modem.

Claims (1)

SUBJECT OF THE INVENTION Connection for modifying the received data signal in the modem and modifying the carrier frequency identification signal, the function of which is to block the transmission of trouble information resulting from the loss of carrier frequency due to the termination of transmission of the message on the link; that the output (601) of the modem receiver demodulator is connected to the input of the valid startbit detection circuit (2) and to the shift register input (6), the exact oscillator output (101) is connected to the sync pulse generator input, output (301) ) from the detection circuit is connected to the second input of the valid startbit detection circuit (Z) and to the input of the carrier frequency identification signal modification circuit (3), the output (201) of the valid startbit detection circuit (2) being connected to the controller input ( 4) «working apartment, whose output (401) is connected to input no a bit counter (5), the second input of which is the output of the synchronization pulse generator (1), the output (501) of which is connected to the zero input of the byte processing controller (4), the other output of which is further connected to the circuit inputs. 2) for detecting a valid startbit, a carrier frequency modification signal (3) and a synchronization pulse generator (1), the output (302) of the carrier identification signal circuit (3) being connected to the modem logic and further connected the gate of the shift register (6) 'whose output (602) is connected to the modem logic.