JPH0728301B2 - Signal transmission method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a contention-type signal transmission method capable of transmission from any station.

In particular, the present invention relates to a signal transmission method capable of increasing the transmission distance without lowering the transmission speed.

[Prior Art] First, a transmission system in which a conventional signal transmission method is used will be described with reference to FIG.

FIG. 3 is a block diagram showing a transmission system in which a conventional signal transmission method is used.

In FIG. 3, the transmission system includes a central control and monitoring device (hereinafter referred to as a master station) (1) and a plurality of units connected to the master station (1) via a transmission line (2) having a length l1. Terminal control monitoring device (hereinafter referred to as a slave station) (3), (4),
It is composed of (5) and (6). The slave station (6) is separated from the master station (1) by a distance l1.

Next, a conventional signal transmission method will be described with reference to FIG.

FIGS. 4A to 4E are timing charts showing the operation of the conventional signal transmission method.

In FIG. 4, ↑ indicates a sampling position.

For example, the master station (1) has a higher priority than the slave station (6),
A case where the master station (1) starts transmission before the transmission signal of the slave station (6) reaches the master station (1), that is, a signal collision occurs will be described.

When the slave station (6) determines that the transmission path (2) is free, it transmits the transmission signal shown in FIG. 4 (a) to the transmission path (2). This transmission signal has a pulse width of W1,
If the pulse width is the same as the priority part of the pulse train of "LHLHH"
It has a data part of W1.

The master station (1) receives the signal from the slave station (6) shown in FIG. This time delay α is proportional to the distance l1 of the transmission line (2).

The master station (1) determines that the transmission path (2) is free before β when the signal from the slave station (6) is received,
The transmission signal shown in FIG. 7C is transmitted to the transmission line (2).
This transmission signal has a pulse width of W1, and has a priority part of the pulse train of "LHLLH" and a data part of W1 having the same pulse width.

The slave station (6) receives the signal from the master station (1) shown in FIG.

The slave station (6) combines the transmission signal of its own station shown in (a) of the figure and the reception signal from the master station (1) shown in (d) of the figure as shown in (e) of the figure. (Logical sum of L). When the slave station (6) determines that it does not have the transmission right based on the combined signal, that is, when the priority section of its own station is H, the combined signal has the priority section of L, and stops transmission, and then receives. Concentrate on. The part indicated by the dotted line in FIG. 7E is the signal from the master station (1).

When contention occurs, the slave station (6) that cannot be transmitted due to its low priority is appropriate because the sampling position for bit determination is not the transmitted signal but the transmitted signal. Not a good sampling position. Since the sampling position is determined by the start point of the signal, the longer the distance of the transmission line (2), the larger the deviation.

Further, the pulse width may be widened in order to increase the distance of the transmission line (2) without causing an error in bit determination, but in that case, the transmission speed is reduced.

[Problems to be Solved by the Invention] The conventional signal transmission method as described above has a problem that the distance of the transmission path cannot be increased.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to obtain a signal transmission method capable of increasing the distance of a transmission line without slowing the transmission speed.

[Means for Solving the Problems] A signal transmission method according to the present invention is a contention type signal transmission method capable of transmitting from any station, and there is no transmission request of the own station or there is a transmission request, and a transmission path. If there is a signal in, first receive the fixed length priority part,
Next, when there is a signal change from the start of the data section, the step of resetting the sampling position to receive the data section, and when there is a transmission request of the own station and the transmission path is vacant, First, while checking for each bit whether or not the signal on the transmission path is a transmission signal of its own station, the priority section of the first pulse width determined by the length of the transmission path is transmitted. When a signal collision occurs in the step of transmitting a data portion having a second pulse width narrower than the first pulse width, and when there is a transmission request from the local station and the transmission path is free. A step of synthesizing a transmission signal of its own station and a reception signal from another station, and devoting itself to the reception operation when it is determined that there is no transmission right based on the priority portion of the synthesized signal.

[Operation] In the present invention, when there is no transmission request of the own station or there is a transmission request and there is a signal on the transmission path, the fixed-length priority part is first received, and then the data part When there is a signal change from the start, the sampling position is reset and the data section is received. Further, when there is a transmission request from the own station and the transmission line is vacant, first, whether or not the signal on the transmission line is the transmission signal of the own station is checked bit by bit and the transmission line of the transmission line is checked. The priority portion of the first pulse width determined by the length is transmitted, and then the data portion of the second pulse width narrower than the first pulse width is transmitted. Further, when there is a transmission request from the own station and the transmission path is free, when a signal collision occurs, the transmission signal of the own station and the reception signal from another station are combined, and this combination is performed. When it is determined that there is no transmission right based on the priority portion of the signal, the reception operation is focused.

[Embodiment] The operation of the embodiment of the present invention will be described with reference to FIGS. 1 and 2.

1 (a) to 1 (e) and FIG. 2 are a timing chart and a flow chart showing the operation of an embodiment of the present invention.

The configuration of the transmission system in which the embodiment of the present invention is used is
This is the same as the transmission system in which the conventional example is used. However, the length of the transmission path (2A) is l2 (> l1).

First, the reception and transmission operations of the master station (1) and the slave station (6) will be described with reference to flowcharts.

In steps (10) to (15), the reception operation is performed when there is no transmission request of the own station or there is a transmission request and there is a signal on the transmission path (2A). First, the priority part having a predetermined length is received, the sampling position is changed, and the data part is received. That is, the sampling position is reset when the signal changes from the start of the data section (H → L or L → H).

Further, in steps (15) to (20), the transmission operation is performed when there is a transmission request from the local station and the transmission path (2A) is free. First, the priority order part is transmitted while checking bit by bit whether or not the signal on the transmission path (2A) is the transmission signal of the own station. When transmitting the data part, the transmission bit width is made narrower than that of the priority part.

Here, steps (10) → (15) → (16) → (17) →
The case of (12) → (13) → (14), that is, the case where a signal collision occurs will be described.

For example, the master station (1) has a higher priority than the slave station (6),
A case where the master station (1) starts transmission before the transmission signal of the slave station (6) reaches the master station (1) will be described.

When the slave station (6) determines that the transmission path (2A) is free, it transmits the transmission signal shown in FIG. 1 (a) to the transmission path (2A). This transmission signal has a pulse width of W2 (> W1) and a pulse width of "LHLHH" in the priority section of the pulse train.
It has a data part of W3 (<W2). The pulse width W2 is determined by the length l2 of the transmission line (2A).

The master station (1) receives the signal from the slave station (6) shown in FIG. This time delay α is proportional to the distance l2 of the transmission line (2A).

The master station (1) judges that the transmission path (2A) is free in β before the time when the signal from the slave station (6) is received,
The transmission signal shown in FIG. 7C is transmitted to the transmission line (2A).
This transmission signal has a pulse width of W2, and has a priority part of the pulse train of "LHLLH" and a data part of which the pulse width is W3.

The slave station (6) receives the signal from the master station (1) shown in FIG.

The slave station (6) combines the transmission signal of its own station shown in (a) of the figure and the reception signal from the master station (1) shown in (d) of the figure as shown in (e) of the figure. (Logical sum of L). The slave station (6) stops the transmission at the time when it judges that there is no transmission right based on the combined signal, that is, when the priority portion of its own station is H, the priority portion of the combined signal is L, Focus on receiving. Then, the sampling position is reset from the start of the data section. The part indicated by the dotted line in FIG. 7E is the signal from the master station (1).

According to the embodiment of the present invention, as described above, the pulse width of the data part is made shorter than the pulse width of the priority part of the transmission signal, and the bit position sampling position and sampling period of the data part are received. Since it was reset at the same time as the start, the transmission line (2
The effect of being able to lengthen the distance of A) and reducing errors in the priority part and the data part is exerted.

In the above embodiment, the data part has a delay of the length of the transmission line (2A) at worst, but the priority part has a delay of about twice the length of the transmission line (2A) in the worst case. Therefore, the pulse width of the data part may be half the pulse width of the priority part.

[Effects of the Invention] As described above, the present invention is a contention-type signal transmission method capable of transmission from any station, and there is no transmission request of the own station or there is a transmission request and there is a signal on the transmission line. In this case, first, the fixed-length priority order part is received, then the step of resetting the sampling position at the time when there is a signal change from the start of the data part and receiving the data part, If there is a transmission request and the transmission line is vacant, first, it is determined by the length of the transmission line while checking whether the signal on the transmission line is the transmission signal of the own station bit by bit. Transmitting a priority portion having a pulse width of 1 and then transmitting a data portion having a second pulse width narrower than the first pulse width; Smell when the road is free Then, when a signal collision occurs, the transmission signal of the own station is combined with the reception signal from another station, and the reception operation is performed at the time when it is determined that there is no transmission right based on the priority section of the combined signal. And the step of devoting to the above, there is an effect that the distance of the transmission path can be lengthened without slowing the transmission speed.

[Brief description of drawings]

FIG. 1 is a timing chart showing an embodiment of the present invention, FIG. 2 is a flow chart showing an embodiment of the present invention, and FIG. 3 is a block diagram showing a transmission system in which a conventional signal transmission method is used. FIG. 4 is a timing chart showing a conventional signal transmission method. In the figure, (1) ... Central control monitoring device (master station), (2), (2A) ... Transmission line, (3) to (6) ... Terminal control monitoring device (slave station). In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a contention-type signal transmission method capable of transmitting from any station, if there is no transmission request of the own station or there is a transmission request and there is a signal on the transmission line, first, a fixed length Receiving the priority part, and then receiving the data part by resetting the sampling position when there is a signal change from the start of the data part; If it is empty, first, while checking whether the signal on the transmission path is the transmission signal of the own station bit by bit, the priority section of the first pulse width determined by the length of the transmission path is set. Transmitting, and then transmitting a data portion having a second pulse width narrower than the first pulse width, and a signal is transmitted when there is a transmission request from the local station and the transmission path is free. When a collision of Combining the transmission signal of the station and the reception signal from another station, and concentrating on the reception operation at the time when it is determined that there is no transmission right based on the priority portion of the combined signal. Signal transmission method.