JPS58131848A - Detection system of data bus collision - Google Patents

Abstract

PURPOSE:To detect surely, the collision of communication signal on a bus from a frequency spectrum of a detection signal, by detecting the signals on the data bus via a nonlinear reception circuit. CONSTITUTION:Signals on the data bus are received at an amplifier 11, led to a reception circuit R and applied to a comparator 12 of the nonlinear circuit setting a prescribed threshold value. The comparator 12 shapes in terms of wave the reception signal to change the pulse width depending on whether the reception signal is in collision or not. This output signal is applied to a BPF13 to extract the frequency spectrum component having the signals only. The extracted spectrum component is applied to the 2nd comparator 14 to discriminate the signal level of the frequency specturm to a prescribed threshold value. When the output signal level of the BPF13 exceeds a prescribed threshold value, a signal S detecting the collision is outputted and the collision of the communication signal is detected surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a data bus collision detection method that can reliably detect collisions of signals communicated between a plurality of station units on a data bus. Background] Distributed processing networks have large system independence;
Maybe host computer 1? , - It has great advantages such as a reduction in the role of network operators and high reliability of the network. For this reason, it has rapidly become popular with the spread of electronic computer systems, and its usefulness is attracting attention. However, in this distributed processing network, a completely distributed type without a host computer is ideal, but since communication control is not performed by the host computer, it is extremely difficult to detect and prevent signal collisions on the data bus. This is an important issue.

FIG. 1 shows the relationship between a data path line 1 and a station 2 that constitute a network. The stage controller 2 includes a transmitter 3 that transmits a transmission signal T to the data bus line 1, and a receiver 4 that receives the signal on the data bus line 1. Moreover, the above transmission signal T is
The signal is led to a collision detection circuit 6 via a delay circuit 5, and is compared with the received signal R received by the receiver 4. The collision detection circuit 6 detects a collision of signals in the data path line 1 by comparing the signals. That is, the collision detection circuit 6 determines that when there is no signal on the data path line 1, the transmitted signal A from the transmitter 3 is also detected in the receiver 4, and that the received signal at this time is the same as the transmitted signal. the fact that there is already another signal B on data path line 1.
exists, the received signal becomes (A+B) υ
, is different from the transmitted signal, a collision of signals on the data bus line 1 is detected.

Note that the delay circuit 5 compensates for the propagation delay of the signal via the transmitter 3 and receiver 4. The collision detection circuit 6 is generally realized by an exclusive OR circuit or the like.

[Problems with background technology]

However, such collision detection can only detect communication collisions between the own station and other stations.

Unfortunately, it is impossible to detect any communication collision between other stations occurring on the data path line 1. Moreover, in order for the collision detection circuit 6 to perform accurate detection processing, it is necessary to define the delay characteristics of the delay circuit 5 with high precision, which has the disadvantage of being extremely difficult to realize. Ta.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and its purpose is to provide a data bus collision detection method that can reliably detect collisions of communication signals on a data bus. .

[Summary of the invention]

The present invention provides that when a signal on a data bus is detected through a nonlinear receiving circuit, the frequency spectrum of the detected signal is different depending on whether the signals are colliding on the data bus or not. Focusing on this, the collision of signals on the data bus is detected by detecting changes in the frequency spectrum of the detection signal.

〔Effect of the invention〕

Therefore, according to the present invention, since collisions are detected from changes in the frequency spectrum of signals detected via a nonlinear receiving circuit, there is no need for a delay circuit that is time-adjusted with high precision as in the conventional case. Furthermore, even in a network where the signal propagation time is undefined depending on the transmission path length, collision detection can always be performed reliably and easily. Furthermore, it is possible to detect communication collisions between other stations on the data bus, which has a great practical advantage.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 2 shows that the base width is 52.5 n+see and 6
25n81! This figure shows the frequency spectrum of a 10 Mblt/see RZ siram signal. Spectrum A shown by the solid line in FIG. 2 is a signal spectrum with a pulse width of 52.5 n5ec, and 1152
．． Spectrum B, shown by the dashed line, is a signal spectrum with a pulse width of 62.5 naec, which is 1/62.5 n5ec, or 19 MHz spacing. yields a spectral null.Also, the line spectrum C is
This appears due to the 10 Mbit/sec repetition of each of the above signals, and is unrelated to the pulse width of the signal.

As shown in this spectral relationship, the frequency spectrum of the signal has a close relationship to the pulse width of the signal. On the other hand, the pulse width of signals communicated via a data bus is usually determined by the network.

When a signal collision occurs on the data bus, the pulse width of the signal that caused the collision changes compared to the pulse width of the original signal. This results in a change in the frequency spectrum of the signal.

The present invention has been made based on this basis.

FIG. 3 shows an example of the configuration of a collision detection circuit that implements the embodiment method.

In FIG. 3, signals on the data bus are received via amplifier 1. This received signal is guided to a 6-stage receiving circuit (not shown).

On the other hand, the received signal is a controller with a predetermined threshold set.
L/-Evening 12 The second day is over. This comparator 12
As is well known, the circuit exhibits nonlinear input/output characteristics and functions as a nonlinear receiving circuit.

The comparator 12 shapes the waveform of the received signal. Therefore, when the received signal is one that has caused a collision,
When this is not the case, the pulse width of the output signal of the comparator 12 changes. However, the output signal of this commutator 12 is passed through a predetermined band pass filter (BPF) 13.
is led to the second comparator 14 via. Above B
The PF 13 has a sharp filter characteristic that selectively passes only the frequency component at the null point of the signal frequency spectrum when the signals on the data bus collide. Therefore, BPF J 3 extracts only the frequency spectrum components of the signal detected via comparator 12. The second comparator 14 discriminates the signal level of the frequency spectrum formed through the BPF 13 with respect to a predetermined threshold value. In this case, when the output signal level of the BPF 13 exceeds the threshold, the constrictor 14 generates a signal S indicating that a collision has been detected.

For the collision detection circuit configured in this way, there are now two stations on the data bus as shown in Fig. 4(,),
(If the signals are being transmitted as shown in ω, these signals will overlap each other on the data bus, resulting in a signal waveform as shown in Figure 4(c). However, this 4th
The signal waveform itself shown in Figure (c) is as shown in Figures (a) and (b).
), their frequency spectra are basically no different from the frequency spectra of the signals shown in FIGS. 3(a) and 3(b).

However, in order to focus on the pulse width of the signal on the data bus, when the signal is detected non-linearly via the converter 12, the received signal R is determined by the threshold value vth as shown in FIG. 4 (cJ). Separately, the waveform is shaped to obtain a detection signal as shown in Figure 4(a).Therefore, the frequency spectrum of the nonlinearly processed detection signal is different from the frequency spectrum of the signal that caused the collision. However, even if a signal that does not cause a collision on the data bus is subjected to nonlinear processing, its pulse width does not change, so the frequency spectrum is the same as that of the signal on the data bus.

The A' pulse width and the frequency spectrum of the signal detected through the controller 12, which is a nonlinear circuit, change depending on whether or not a signal collision has occurred. Therefore, since the BPF 13 detects only the frequency components that constitute the signal's unique frequency spectrum, and the frequency components that would cause a spectral null when there is no collision, when a collision occurs on the data bus, Since the spectral null point of the detected signal changes, a signal with a large level will be generated as the output of the BPF 13. Therefore, the output signal level of this BPF 13 is
By detecting collisions on the data bus, it is possible to reliably detect collisions on the data bus. Furthermore, in the 9-line method, it is only necessary to detect a change in the frequency spectrum of a received signal detected by nonlinear processing, so the detection circuit can be configured very simply.

In this way, according to this method, collision detection is performed by detecting the frequency spectrum of the signal on the data bus without using the own transmission signal, so it is possible to effectively detect communication collisions between other stations. Can be detected. Furthermore, unlike conventional methods, the transmission signal of the own station is not used, so there is no need for delay circuits that require complicated adjustments, and there is no delay in signal transmission due to connection between the data bus and the station. It has great practical advantages, such as not causing any problems.

Similarly, the present invention is not limited only to the above embodiments. For example, as a nonlinear receiving circuit, not only a commutator constructed using active elements, but also a flange circuit using a diode as a passive element, or other structures can be used. Furthermore, it is of course possible to perform not only the bus width shaping but also other nonlinear processing. Furthermore, it is also possible to detect a null point in the frequency spectrum of a signal detected through a nonlinear circuit, and perform collision detection from the frequency change. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the conventional collision detection method, Fig. 2 is a diagram showing the relationship between the base pulse width of the signal and its frequency spectrum, and Fig. 3 is a diagram of the collision detection circuit realizing the method of the present invention. A configuration diagram of an embodiment, and FIGS. 4(a) to 4(d) are signal waveform diagrams for explaining the embodiment. 11...Amplifier, 12...Constructor (non-i-type circuit), 13...Band pass filter (BPF), 24
...Comparator (level detection). Applicant's agent Patent attorney Takehiko Suzue 11- Figure 1 Figure 4

Claims (2)

[Claims] (1) A data bus collision detection method, characterized in that a signal on a data bus is detected through a nonlinear receiving circuit, and a collision of communication signals on the data bus is detected from the frequency spectrum of the detected signal. (2) Detection of the frequency overlap of the detection signal via the nonlinear receiving circuit is performed by extracting the detection signal via a bandpass filter and determining the level of the frequency component. The data bus collision detection method described in scope 1.