JPH06103885B2 - Communication control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous control of a communication control device, which enables a plurality of devices to be connected to each other and to transfer information to each other.

Conventional Technique A conventional technique will be described with reference to FIGS. 4 to 7.
FIG. 4 is a diagram showing a configuration example of a network to which the present invention is applied, FIG. 5 is a diagram showing a configuration example of a communication control device according to the present invention, and FIG. 6 is a conventional home bus control. FIG. 7 shows a signal waveform by synchronization control on the channel, and FIG.
It is a figure which shows the relationship between the collision detection point and the delay on a transmission line at the time of the synchronous processing shown in FIG. In the communication specification on the home bus control channel, there is a synchronization recovery monitoring time, and during that period,
When detecting the start of transmission from another communication control device, the communication control device holding the message to be transmitted can start the transmission in synchronization with the signal. In the network shown in FIG. 4, the delay on the transmission line between the terminals [A] 41 and [B] 42 is α, and the terminal [B] 42 detects a signal from another terminal during the synchronization recovery monitoring time. Let β be the time required to transmit its own start bit. In FIG. 6, (61) shows the output pulse waveform to the control channel of the terminal [A] 41, (62) shows the input pulse waveform from the control channel of the terminal [A] 41, and (63) shows the terminal [B]. ] 42 shows an input pulse waveform from the control channel, and (64) shows an output pulse waveform from the terminal [B] 42 to the control channel. The time T1 until the output of the terminal [A] 41 is input to the terminal [B] 42 holding the transmission message during the synchronization recovery period is the delay α on the bus.
It's time. After detecting the input, the terminal [B] 42 also starts transmitting the electronic message after T2 time (β time) has elapsed. The transmission from the terminal [B] 42 reaches the terminal [A] 41, and further T3 time (α time of delay on the bus) elapses before the collision occurs. Therefore, the terminal [A] 41 can detect the collision with the terminal [B] 42 during the period T4 (transmission start [2α + β]).
After the hour, for [L / 2- (2α + β)] hours. However,
L has a 1-bit length, and in the case of a home bus system, the pulse waveform is DUTY50%, so the pulse output period is L / 2.
Becomes ). On the other hand, at the terminal [B] 42, the terminal [A]
The collision with 41 can be detected during T5 time ([L / 2- (α + β)] time) immediately after the start of transmission. This relationship similarly appears in all subsequent bits, such as T4 = T9, T5 = T10. Letting P be the collision detection point, the above relationship among α, β, and P is expressed by the following equation.

2α + β ≤ P ≤ L / 2 ...... 0 ≤ P ≤ L / 2- (α + β) ...... Also, when transmission is started at the same time, a delay of α time occurs between them, so [α ≤ P ≤ L / 2 ], But this is
Included in the above formula. Even when receiving a telegram, unless the bit detection point is set in consideration of the above contents, a state in which the telegram on the bus cannot be received correctly occurs. Therefore, from the above, the following formula is established as the range of the collision detection point at the time of transmission and the bit detection point P at the time of reception.

2α + β ≤ P ≤ L / 2- (α + β) ...... The time β required for detecting a signal from another terminal and transmitting its own start bit constitutes the processing content in the transmission / reception control processing unit and the control processing unit. The value varies depending on the performance of the microcomputer. In the case of a device intended for an inexpensive household product such as a home bus system, a low-priced device within the standard limit is selected rather than a high-performance and high-priced device. Therefore, according to the standard of home bus system, the maximum value of β is L / 8.
Is specified. From this, the following equation holds as the range of P.

2α + L / 8 ≦ P ≦ (3 × L) / 8−α ... The relationship between P and α in this equation is shown in the shaded area in FIG. The home bus standard specifies L / 4 as the value of P. When the value of P is L / 4, the delay range on the bus is L / 16 or less as is clear from FIG. In the case of the home bus system, since L≈104 μsec, α ≦ 6.5 μsec. At present, the value of 6.5 μsec of the delay on the bus is not always sufficient, and considering the case where the communication specifications similar to the home bus system are applied to the super bus system higher than the home bus system, the cable length and The value of this delay increases due to the expansion of the number of connected devices, etc., and the current communication control device cannot deal with it as it is. The maximum of P point is (3 x L) / 8
≈ (L / 4 + L / 8), and the detection margin is about 13 μsec. This value is a processing time of several steps in a 4-bit or 8-bit microcomputer, and can be said to be barely good when the point P is detected by a timer interrupt or the like.
Therefore, in order to inexpensively configure the control processing unit and application control of the communication control device with a microcomputer, the internal processing specifications become complicated.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention provides expandability to an inexpensive communication control device such as used in a home bus system as shown in the conventional example, and improves performance in terms of internal processing specifications. Is an issue.

Means for Solving the Problems In order to solve the above-mentioned problems, a synchronization control processing unit of a communication control device in a system in which a plurality of terminals each including a communication control device that transmits and receives information is connected to a synchronization carrier from another terminal. The width of the self-synchronization carrier (self-start pulse) transmitted when (start pulse) is detected is shortened by the amount of internal processing time, and the synchronization carrier on the transmission line is confirmed for a certain period of time before the self-synchronization carrier (self-start pulse) is output. When the carrier is not of a fixed format, the synchronous carrier of a fixed length is transmitted without shortening the width of the self-synchronized carrier (self-start pulse) to be output.

Effect The present invention, by the above-mentioned configuration, allows a margin for synchronous control of the communication control device, and can be easily applied to a system of a larger scale that complies with the same communication specifications,
Since the internal processing has a margin, it has an effect that it can be applied to a terminal that requires a more complicated application.

Embodiment An embodiment according to the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is a diagram showing an example of signal waveforms at the time of synchronous control according to the present invention on a home bus control channel, and FIG.
FIG. 3 is a diagram showing a relation between a collision detection point and a delay on a transmission line at the time of synchronization processing shown in FIG. 3, and FIG. 3 is a diagram showing an example of a signal waveform when an abnormal synchronization carrier is detected at the time of synchronization control according to the present invention. FIG. 4 is a diagram showing a configuration example of a network to which the present invention is applied, and FIG. 5 is a diagram showing a configuration example of a communication control device according to the present invention. As described in the description of the conventional example, in the communication specifications on the home bus control channel, the communication control device that has the synchronization recovery monitoring time and holds the telegram to be transmitted during that period is different from other communication control devices. When the start of transmission is detected, the transmission can be started in synchronization with the signal. In the network shown in FIG. 4, the delay on the transmission line between the terminals [A] 41 and [B] 42 is α, and the terminal [B] 42 detects a signal from another terminal during the synchronization recovery monitoring time. Let β be the time required to transmit its own start bit. In Fig. 1, (11) shows the output pulse waveform to the control channel of terminal [A] 41, (12)
Is the input pulse waveform from the control channel of terminal [A] 41, (13) is the input pulse waveform from the control channel of terminal [B] 42, and (14) is the output to the control channel of terminal [B] 42. The pulse waveform is shown. It takes a delay t1 time (α time) on the bus until the output of the terminal [A] 41 is input to the terminal [B] 42 which holds the transmission message during the synchronization recovery period. At terminal [B] 42, t2 time (β time) after detecting input
After the lapse of time, he also starts sending a message. This terminal [B] 42
Further, t3 (α time) elapses before the transmission from the terminal reaches the terminal [A] 41 and a collision occurs. At this time, the terminal [B] 42
Then, it detects that the output is due to competition processing, and sends the pulse width at the start as β shorter than the width when it is transmitted alone (t5). Therefore, from the next bit, the terminal [B] 42 can confirm the collision in the entire range of the bit, and the terminal [A] 41 detects 2α from the start of the bit.
After the time, collision can be confirmed by the time of L / 2.
Letting P be the collision detection point, the above relationship can be expressed by the following equation.

2 α ≤ P'≤ L / 2 ...... '0 ≤ P'≤ L / 2 ......' Also, if transmission is started at the same time, a delay of α time occurs between them, so [α ≤ P'≤ L / 2], which is included in the above formula. Even when receiving a telegram, unless the bit detection point is set in consideration of the above contents, a state in which the telegram on the bus cannot be received correctly occurs. For this reason,
From the above 'and', the following equations are established as the range of the collision detection point at the time of transmission and the bit detection point P'at the time of reception.

2α≤P'≤L / 2 ... 'The relationship between P'and α in this equation is shown in the shaded area in FIG. The home bus standard specifies L / 4 as the value of P. When the value of P'is 4 / L, the delay range on the bus is 3L / 64 or less, as is apparent from FIG. For home bus system L ≈ 1
Since it is 04 μsec, α ≦ 10 μsec. Traditionally,
The value of the delay on the bus was 6.5 μsec. When a coaxial cable is used as the transmission line, this delay difference is about 3.5 μsec.
(10 μsec-6.5 μsec) corresponds to a cable length of about 350 m, and can be applied to a larger system without any change in the communication control device, which is easy. Also, P '
The maximum of the points is (7 × L) / 16≈ (L / 4 + 3L / 16), and the detection margin is about 19.5 μsec. According to conventional specifications about 1
It is 3 μsec, which means that a 6.5 μsec margin has been created. As a result, even when a 4-bit or 8-bit microcomputer is used for the control processing unit, the control processing unit and the application control of the communication control device can be easily and inexpensively configured by the microcomputer, because there is a margin. It becomes possible to do.

Further, according to the present invention, since the output width of the sync carrier is intentionally shortened, if the normal sync carrier is not detected, the reception of the third communication control device is normally performed. I will not be lost. For example, as shown in FIG. 3, the sync carrier is confirmed again immediately before the self-sync carrier is output after t1 + t2 time has elapsed after the input of the sync carrier is detected. Sano synchronization carrier is output. As a result, even if the detected synchronous carrier is abnormal, it is possible to transmit a normal telegram.

EFFECTS OF THE INVENTION According to the present invention, it is possible to allow a margin for synchronous control of a communication control device, facilitate application to a system of a larger scale that complies with similar communication specifications, and allow a margin for internal processing. Therefore, it has an effect that it can be applied to a terminal that requires a more complicated application.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of signal waveforms at the time of synchronous control according to the present invention on a home bus control channel, and FIG.
FIG. 3 is a diagram showing a relation between a collision detection point and a delay on a transmission line at the time of synchronization processing shown in FIG. 3, and FIG. 3 is a diagram showing an example of a signal waveform when an abnormal synchronization carrier is detected at the time of synchronization control according to the present invention. FIG. 4 is a diagram showing a configuration example of a network to which the present invention is applied, FIG. 5 is a diagram showing a configuration example of a communication control device according to the present invention, and FIG. 6 is a conventional home bus control channel. FIG. 7 is a diagram showing a signal waveform by synchronous control above.
FIG. 6 is a diagram showing the relationship between the collision detection point and the delay on the transmission line during the synchronization processing shown in FIG.

Claims (2)

[Claims] 1. In a system to which a plurality of terminals having a communication control device for controlling transmission / reception of information are connected, the synchronous carrier is detected when a synchronous carrier (start pulse) is detected on a transmission line during a synchronous processing period at the time of transmitting a message. A communication control device having a synchronization control processing unit for controlling the transmission start in synchronization with, and for shortening the self-synchronization carrier (self-start bit pulse) width by an internal processing time for transmission. 2. A synchronous carrier on a transmission line is detected for a certain period of time before transmission of the self-synchronizing carrier, and when the detected synchronous carrier is not a carrier of a predetermined format, a predetermined self-synchronizing carrier width is output without shortening. The communication control apparatus according to claim 1, further comprising a synchronization control processing unit that transmits a self-synchronization carrier having a length of.