JPS626551A - Frequency multiplex bus type transmission system - Google Patents

Abstract

PURPOSE:To transmit a signal even at a heavy load while utilizing an idle frequency band by combining an algorithm selecting an idle bus and sending a signal with a conventional back-off algorithm. CONSTITUTION:A bus supervisory equipment 41 checks whether a bus is idle at a present band F1 or not and when the bus is idle, the data is sent immediately and when not idle, the band setting is changed over and a bus supervisory equipment 42 checks whether or not the bus is idle. when an idle bus is found out, for example, the bus is idle at a band F1, a CPU 5 selects a modulator 31 by using a band changeover switch FC to execute transmission. The bus is supervised respectively by the bus supervisory equipments 41, 42 at both the frequency bands F1, F2 in the reception and when the transmission data to the own station is detected, the other bus supervisory equipment is stopped to apply reception only at the band at the presence of the transmission to the own station.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention defines computers, various intelligent terminals, peripheral devices, etc. as stations (hereinafter also referred to as stations), and connects them to each other through one common signal line (bus). ), and relates to a frequency multiplex bus type transmission system in which frequency multiplexed transmission and reception data are transmitted by connecting in parallel via the bus.

[Conventional technology]

In general, networks are bus-type due to their form.

It is classified into ring type, tree type, star type, etc., and among these, bus type networks are: (1) It is easy to add and delete nodes (Mode) and is highly flexible.

(2) High reliability because failure of one station does not affect the entire network.

(3) The access control algorithm is relatively simple.

It has the following advantages.

[Problem that the invention seeks to solve]

On the other hand, if a token-passing algorithm is used that sequentially passes the access phase to each station using a specific signal called a talk, control becomes quite complex.
The problem with this system is that the transmission data from multiple stations collides, resulting in reduced efficiency during high loads.

Therefore, it is an object of the present invention to provide a transmission system using a bus network that reduces the reduction in efficiency of the bus network during high loads and is efficient even during high loads.

[Means for solving problems]

A monitoring means for monitoring a common bus in a plurality of frequency bands for each station, a transmitting means and a receiving means for selecting an empty frequency band on the bus and transmitting and receiving data, and based on the output of the monitoring means Carano. A control means for controlling the transmission and reception means of the lever is provided.

[Effect]

Figure 1 is a main diagram that best represents the features of this invention. In the figure, 51 to 3n each indicate the frequency band B.
41 to 4n are bus monitoring devices that monitor the frequency band and data on bus 1, 51 to 5n are control units (CPUs) such as microcomputers, and 61 to 6n are modems that can be switched from and1 to Bandm. The transmitter and 71 to 7n are receivers, and each of these devices is provided corresponding to each station (21 to 2n), and by switching multiple frequency ranges and combining with the bank-off algorithm, efficiency is maintained even during high loads. This allows for good transmission. Note that the bank-off algorithm is a well-known technique for reducing the frequency of retransmission of colliding data to avoid an unstable phenomenon in which throughput (actual transmission capacity) decreases.

〔Example〕

FIG. 2 is a block diagram showing an embodiment of the present invention.

This shows one station consisting of a plurality of stations installed in parallel on a bus 1, including a modem 3 capable of switching between two frequency bands F1 and F2, bus monitoring devices 41 and 42,
It is composed of a CPU 5 that performs various controls, a transmitter 6, a receiver 7, and a timer (backoff timer) 8 that measures retransmission time.

The CPU 5 sends a frequency band switching signal FC to the modem B.
10,000 to transmit data TD and a transmission request signal TC to perform data transmission, and transmit a reception request signal RC to the receiver 7. and receives the received data RD. Also,
A start/stop signal SR is sent to the bank-off timer 8, and a TP multiplication signal is received to notify time-up.

A specific example of the modem is shown in FIG. The data from the transmitter 6 is transferred to the selector switch 35 by the signal FC from the CPU 5.
is switched and supplied to modulator 31 (Fl) or 32 (F2), and data is sent to bus 1 in frequency band F1 or F2. On the other hand, data received from bus 1 is received from bus 2 at the same time.
Two demodulators 33 (Fl) and 54 (F2) K are supplied, respectively.

Demodulate data in wavenumber bands F1 and F2. The demodulated data is monitored by bus monitoring devices 41 and 42, respectively, and data addressed to the own station is supplied to the receiver 7. child~
Here, monitoring refers to checking whether there is a data collision during transmission, whether the bus is empty, and whether the data is addressed to the own station.

Note that collisions can be detected, for example, by comparing the transmitted data with demodulated data taken in from the bus, or by changes in the voltage level on the bus, and if the bus is vacant or not, for example, if the bus has changed for a certain period of time or more. It is possible to check whether the data is addressed to the own station or not by comparing the address in the data with the address of the own station. . In addition, the bus monitoring devices 41 and 42 each have signal lines L.
The two stations are connected by a signal line C, and the one that receives data destined for itself first stops the other station by the signal from this signal line, so that only data from one side is supplied to the receiver 7. ing.

When the stopped bus monitoring device returns to the image frequency band monitoring operation according to the reception operation described later, the bus monitoring device receives the signal LS1. The operation is restarted by LS2. Information on whether bus 1 is vacant or not is obtained by sending the signal L01e L O2 to CP.
It can be obtained by reading U5.

The operation of the station will be explained separately during transmission and reception.

(I) Transmission operation FIG. 4 is a flowchart showing the transmission procedure. As an initial setting when resetting the system, the frequency band to be used is set to 10,000, for example, Fl, and the frequency band switching signal F
Switch 35 of modem 3 is switched by C to connect modulator 31 and transmitter 6 (see ■). Bus monitoring device 4
1, check whether the bus is free in the current band F (see ■), and if it is free, send the data immediately (see ■), and if it is not free, switch the band setting (
(Refer to (2)), the bus monitoring device 42 next checks whether or not the bus is vacant in band F2. Similarly below,
Repeat steps ■ and ■ until you find a space. When an empty bus is found, for example, if the bus is empty in the band F1, the CPU 5 switches the modulator 31 by the band switching signal FC.
Select and execute the transmission (see ■). Next, the presence or absence of a collision is checked by the bus monitoring device 41 (see ■), and if there is no collision and there is no data to be transmitted, the transmission is terminated. If there is no collision and there is still data to be sent, return to bus monitoring ■. On the other hand, if there is a collision, the back-off timer 8 is started (see ■), the bus is monitored in other bands (see ■), and if the bus is free, the modulator is switched to that for that band (see ■). ), stop timer 8 and retransmit (see ■). Here, if the bus is not available in that band, it is checked whether the timer has timed up (see [phase]), and if it has timed up, retransmission (2) is executed in the current band. On the other hand, if there is no time-up, until retransmission is executed■,
After repeating step (2) and retransmitting, return to step (2) and repeat the same steps as above.

(I[) Reception Operation FIG. 5 is a flowchart showing the reception procedure. F
Each bus monitoring device 41 and 42 monitors the bus in the image frequency band of 1e F 2 (see ■), and when it detects transmission data to its own station (see ■), the other bus monitoring device (for example, 41 If data addressed to the station is detected, 42) is stopped and reception is performed only in the band that was transmitted to the own station (see ■). If an error occurs during reception, error processing (2) such as sending a retransmission request is performed and the process is terminated, or reception is resumed as in point a (2). If there is retransmission, there are two ways to do it: fixing the band to the current band or searching for a new free band. In the former case, start from ■, and in the latter case, start from ■ as shown by the dotted line @. resume. Also, if there is no error and reception is not completed, restart from ■ or ■. When you return to ■, CP
U5 uses signals L S 1 * L S 2 to restart the stopped bus monitoring device in order to search for data addressed to its own station in the image frequency band. Note that if data is transmitted to the own station in other bands while receiving data in the -10,000 band, this is ignored because the bus monitoring device is stopped. In this case, it is necessary for the transmission source to detect this by detecting no response, etc., and take measures such as retransmission.

Note that although an example in which two frequency bands are used has been described above, this number can be set to any number as long as the control is not complicated, and bus monitoring devices may be provided depending on the number. Not until now.

〔Effect of the invention〕

According to this invention, by combining an algorithm that selects bus vacancies in multiple frequency bands and performs transmission with a normal back-off algorithm, it is possible to perform transmission using vacant frequency bands even during high loads. This not only improves transmission efficiency but also reduces transmission time.

[Brief explanation of drawings]

Figure 1 is the main figure that best represents the features of this invention;
3 is a block diagram showing a specific example of a modem, FIG. 4 is a flowchart for explaining the transmission operation, and FIG. 5 is a flowchart for explaining the reception operation. It is. Code explanation 1...Common bus, 21-2n...Station, 3.31-5n...Modulator/demodulator (modem), 4,41°42, 41-4n- ... Bus monitoring device, 5, 51S-5n control device (CPU), 6,
61~6n...Transmitter, 7.71~7n...
...Receiver, 8...Timer, 31°32...
...Modulator, 35.34 ...Demodulator, 35
・・・・・・Choice switch. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki 3 Figure 21iI! ! Figure 4

Claims (1)

[Claims] A frequency multiplexing bus type transmission system in which a plurality of stations are connected in parallel via one common signal line (bus), transmitting and receiving data mutually through frequency multiplexing, and in which the bus is connected to each station for each station. A monitoring means for monitoring in a plurality of frequency bands, a transmitting means and a receiving means for selecting an empty frequency band on the bus and transmitting and receiving data, and a transmitting and receiving means for transmitting and receiving data based on the output from the monitoring means. and a control means for controlling the frequency band, and when there is a conflict between the transmitted data and the received data, if there is another free frequency band, the data is immediately retransmitted in that frequency band, while if there is no free frequency band, the data is immediately retransmitted. After a predetermined retransmission time, it monitors the time to retransmit in the frequency band it originally transmitted, and searches for another free frequency band, and if the retransmission time reaches the retransmission time before finding a free frequency, it retransmits in the original frequency band. A frequency multiplex bus type transmission system characterized in that if an empty frequency is found before the retransmission time is reached, retransmission is performed in that frequency band.