JPH06291749A - Bus repeater - Google Patents

Abstract

PURPOSE:To facilitate design, to improve versatility and to extend a bus with a stable operation even in a high transmission rate by providing with a control means for cancelling the interruption of a transmission route to a relay transmission line side by completing signal transmission to a bus side. CONSTITUTION:Control circuits 5 for respective signal lines based on bus standards such as SCSI and GPIB are provided in the inside of this repeater 1 and output signals to a bus signal line side are monitored by the control circuits 5. Then, when the output signals to the bus signal line side are present, control is performed so as not to output sneaked-in reception signals to the relay transmission line side and the leakage of signals in the relay transmission lines 4 of a full-duplex system is prevented. Also, the relay transmission lines 4 is the parallel optical fiber cables of the full dulplex system for which optical fibers are parallelly provided. By relay via the parallel optical fiber cables, high-quality long distance transmission is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus relay device for extending a half-duplex bus such as SCSI or GPIB using a relay transmission line, and particularly to communication between high-speed and large-capacity computers. It is suitable for data transfer.

[Prior art]

Conventionally, a half-duplex bus represented by standards such as SCSI and GPIB has been widely used for communication and data transfer between a computer and peripheral devices. When trying to extend a device using such a bus communication method via a relay transmission line at the user's request, using a full-duplex type relay transmission line using optical fibers is resistant to noise and supports high transmission rates. This enables long-distance transmission.

In order to realize this, a signal received from the relay transmission line side circulates inside the full-duplex type relay device to the relay device for connecting the bus standard device and the relay transmission line, It is necessary to prevent oscillation caused by leakage of the received signal sent to the relay transmission line on the transmission side.

As a conventional technique for extending the half-duplex bus by a full-duplex communication transmission line, there is, for example, Japanese Patent Publication No. 2-60105 "GPIB repeater". This technology considers the delay time required for the output signal to wrap around from the repeater to the GPIB bus, and when the signal is received from the relay transmission line, determines the transmission route of the received signal from the bus to the relay transmission line side. The present invention relates to a repeater, which is designed to prevent signal leakage to a relay transmission line by cutting off the previous reception start and giving a predetermined delay amount to a trailing edge of a received signal.

However, in the method of preventing signal leakage by determining the delay amount on the side of the relay device as described above, the delay amount is set when the circuit design is changed or when another interface is to be dealt with. There was a problem that we had to start over. Further, when transmitting and receiving an information signal at a high transmission rate through an optical fiber, there is no room for setting the delay amount, and therefore, there has been a problem that precision is required for setting the delay amount.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art and connects a half-duplex bus and a full-duplex relay transmission line to enable high-speed data transfer. It is an object of the present invention to provide a bus relay device that has a simple design, is highly versatile, and can extend a bus with stable operation even at a high transmission rate.

[0007]

According to a first aspect of the present invention, the inside of a relay device used when connecting and extending a half-duplex bus with a full-duplex relay transmission line. Further, a control means is provided for canceling the interruption of the transmission path from the bus to the relay transmission path when the signal transmission to the bus is completed.

According to a second aspect of the present invention, in addition to the first aspect, a function of resetting a transmission path corresponding to a defective state of a signal due to bus relay is provided.

According to the third aspect of the present invention, in addition to the first and second aspects, the transmission of the signal received from the relay transmission line to the bus is blocked from the bus to the relay transmission line. The control means is provided so as not to send a signal to the bus side if the route cutoff from the bus to the relay transmission line does not operate for some reason after starting after the above is confirmed.

According to a fourth aspect of the present invention, the first,
In addition to the second and third aspects, an electric / optical and optical / electrical conversion unit corresponding to each signal of the bus is provided, an optical bus is used as a relay transmission line, and an electric / optical interface is provided to the relay transmission line. Also, an optical / electrical converting means is provided.

[0011]

According to the bus repeater of the present invention, a control means is provided inside the repeater for use in connecting and extending a half-duplex bus by a full-duplex relay transmission line to provide a bus signal. Monitor the condition of the signal to the line side. Depending on the signal state to the bus signal line side, by controlling cutoff / cancellation of the transmission path from the bus side inside the relay device to the relay transmission line side, the sneak of the received signal generated inside the relay device Prevent signal leakage.

[0012]

FIG. 1 is a diagram showing an example of a system configuration in which a bus 2 and a bus 3 are connected via a full-duplex relay transmission line 4 using a relay device 1 embodying the present invention. is there. The bus 2 and the bus 3 to which the present invention is applied are applicable as long as they are half-duplex buses, and for example, buses such as SCSI and GPIB can be applied. In order to actually control the transmission of bus signals to transfer data, etc., control based on commands according to the applied bus standard is necessary, but they are not related to the essence of the present invention. The description is omitted.

Inside the relay device 1, SCSI, GPI
A control circuit 5 is provided for each signal line based on the bus standard such as B. The output signal to the bus signal line side is monitored by this control circuit 5, and the output signal to the bus signal line side is monitored. In some cases, control is performed so that the received signal that spills around is not output to the relay transmission line side, and signal leakage in the full-duplex relay transmission line is prevented.

The relay transmission line 4 in this embodiment is a full-duplex type parallel optical fiber cable in which optical fibers are provided in parallel. High-quality long-distance transmission is realized by the relay using this parallel optical fiber cable. For this reason, the control circuit 5 is provided with an interface corresponding to the optical fiber, but the present invention can be applied to an ordinary coaxial cable or the like by adopting an electrical interface between the relay device and the relay transmission line. Needless to say.

FIG. 2 is a circuit diagram showing an embodiment of the control circuit 5. Reference numeral 51 is an optical / electrical converter for converting an optical reception signal from each optical fiber cable into an electric signal, and 58.
Is an electric / optical converter that converts electric / optical signals transmitted to the optical fiber cable.

In the control circuit 5, the optical / electrical converter 5
The signals of 1 output, the output of the electro-optical converter 58, and the input / output on the bus signal line side are positive logic, and when the signal is received, it is set to the “H” level, and the signal is not received. The case where there is not is described as "L" level.

Considering a reception standby state in which no signal is received from either the relay transmission line side or the bus side, both the output of the optical / electrical converter 51 and the output to the bus signal line are "L". However, these signal lines are input to the reset terminal of the D-type flip-flop 53 through the OR gate 52. The inverted output of the flip-flop 53 is also input to the reset terminal of the flip-flop 53 through the OR gate 52.

If, for some reason, a defective signal state occurs due to bus relay, the flip-flop 53
Even when the output of the flip-flop becomes "H" and the inverted output becomes "L", the flip-flop 53 is automatically reset based on the inverted output input to the reset terminal at that moment. The flip-flop 53 continues to hold the output at "L" and the inverted output at "H". By this control circuit's reset function of the transmission path corresponding to the defective state of the circuit operation due to the bus relay, systematic resetting is not required for the signal fault caused by the relay.

In the reception standby state, the output of the NOR gate 54 is always at the "H" level, and the transmission path from the bus side to the relay transmission path is always held in the transmission enabled state through the AND gate 55. Further, in the transmission path from the relay transmission path to the bus side, the output of the NOR gate 54 is the inverter 57.
Since it is inverted by and input to the AND gate 56, the cutoff state is maintained.

Next, consider the case where there is a received signal from the relay transmission line side and the output of the optical / electrical converter 51 becomes "H". The output of the optical / electrical converter 51 is a flip-flop 53.
The D-type flip-flop 53 latches the "H" level of the data input by the rising transition due to the reception of the signal and the output is set to "H".
The inverted output is set to "L". At this time, flip-flop 5
In No. 3, since the output of the optical / electrical converter 51 is "H", it is not reset even if the inverted output becomes "L".

Therefore, when there is a received signal from the relay transmission line side, the output of the NOR gate 54 becomes "L", so that the signal received from the relay transmission line side to the bus side passes through the AND gate 56 and is passed. Become. At this time, since the output of the AND gate 55 is "L", it is confirmed that the transmission path from the bus side to the relay transmission path side is blocked. This control circuit controls the transmission of the received signal from the relay transmission line side to the bus side after it is confirmed that the transmission route from the bus side to the relay transmission line side has been cut off. Leakage is prevented.

The cutoff state of the signal from the bus side to the relay transmission line side is not released even if the output signal of the optical / electrical converter 51, that is, the reception signal from the relay transmission line side becomes "L", and the bus is not released. The output signal to the signal line becomes "L",
When the signal transmission to the bus side is completed, the flip-flop 53
Is held until it is reset again, and is released when the signal transmission to the bus side is completed.

Next, considering the case where there is a received signal from the bus side, in this case, the state of the flip-flop 53 does not change at all, so the received signal passes through the AND gate 55 as it is, and the electric / optical converter. Since it is converted into an optical signal by 58 and output to the relay transmission line by the optical fiber, data transmission can be performed without being affected by the interruption of the transmission route by the control circuit.

In the control circuit of this embodiment, the NOR gate 5
The signal line input to the AND gate 55 from the output side of 4 plays a role of controlling passage / cutoff of bidirectional signals. However, in addition to the circuit configuration of this embodiment, the transmission line of the present invention can be used. It is possible to control the interruption.

[0025]

According to the invention described in claim 1, full-duplex bus relay transmission becomes possible only by adding a control circuit having a simple structure, and even when a programmable device is used. , Circuit design is possible without considering the internal delay peculiar to the device, it is not necessary to re-examine the delay amount setting each time the circuit design is changed, and it is possible to adapt to other standard interfaces and high frequencies as they are. The range expands.

According to the second aspect of the present invention, the system itself is automatically reset to the defective state caused by the bus relay and the normal transmission path is secured. Although there is no signal received from the path, malfunctions such as the interruption of the transmission path from the bus to the relay transmission path are prevented, and a highly reliable system can be realized.

According to the third aspect of the present invention, even when the route cutoff from the bus to the relay transmission line does not operate for some reason, the signal is not sent to the bus side, so that the oscillation due to the sneak of the signal occurs. It became possible to perform prevention more reliably.

According to the fourth aspect of the present invention, it becomes possible to perform high-quality long-distance transmission by means of parallel optical fibers, and extend the relay transmission line at the request of the user. Very easy to implement.

[0029]

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a bus relay system according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of control means of the present invention.

[0030]

[Explanation of symbols]

 1 relay device 2 bus 3 bus 4 relay transmission line 5 control circuit

Claims (4)

[Claims] 1. A bus relay device for connecting half-duplex busses via a full-duplex relay transmission line, wherein a transmission path from the bus side to the relay transmission line side from the time when a signal from the relay transmission line is received. The bus relay device is characterized in that the bus relay device releases the interruption of the transmission path to the relay transmission path side when the signal transmission to the bus side is completed. 2. The bus relay apparatus according to claim 1, wherein said control means has a transmission path resetting means corresponding to a defective state of a signal due to bus relay. 3. The control means starts transmitting the signal received from the relay transmission path to the bus after the transmission path cutoff from the bus to the relay transmission path is confirmed. 2. The bus relay device described in 2. 4. The control means is provided with electrical / optical and optical / electrical conversion means corresponding to each signal of the bus, and a parallel optical fiber cable is used as a relay transmission line. Bus relay equipment.