JPS603247A - Extending device of standard interface bus - Google Patents

Abstract

PURPOSE:To attain signal transmission between standard interface buses parted remotely by switching the transmission direction of an optical fiber signal transmitted by means of a signal direction switching circuit, and adjusting the difference in signal transmission speed between a digital signal and an optical signal by a transfer control circuit. CONSTITUTION:The optical fiber signal transmitters 3, 4 and the optical fiber cable 10 are provided between the standard interface buses 9, 9. Then the transmission direction of the signal is changed over by the signal direction switching circuit 2, 5. The difference in transmission speed between the digital signal and the optical signal in case of applying parallel/serial conversion to the signal of the standard interface bus cable 10 and transmitting the result with the optical fiber cable 10, is adjusted by a transfer control circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a standard interface bus extension device;
More specifically, the present invention relates to a standard interface bus extension device for extending a standard interface bus whose cable length is limited due to electrical reasons using an optical fiber signal transmission device.

The standard interface bus (hereinafter referred to as GP-IB) is a standard digital bus standard for transmitting data between electronic devices such as measuring instruments, station equipment, calculators, and computers, and is a standard for data transfer between devices and automatic processing. , designed to be compatible with automatic control.

However, with this CP-IB, if the cable length is too long, the characteristics of the transmitted digital signal will deteriorate.
For practical reasons, the cable length is 2m per device.
There is a maximum limit of 20 m.

On the other hand, electronic devices for extending the distance between devices are also commercially available, but they are very expensive.

Furthermore, as mentioned above, the distance limitations caused by electrical reasons can be overcome by extending the distance using optical fiber signal transmission equipment;
Since optical fiber is a unidirectional transmission, it is necessary to switch the signal transmission direction.■ GP-IB path line has 16
However, when converting from parallel to serial and transmitting it using optical fiber, there is a problem that normal transfer control cannot be performed with optical fiber equipment whose signal transmission speed is slower than the signal processing speed of the equipment, and it is still not possible. This invention has not been put to practical use.0 This invention was made by focusing on such conventional problems, and its purpose is to perform bidirectional data transmission using optical fibers, and to An object of the present invention is to provide an excellent standard interface bus extension device that can also perform transfer control.

For the above purpose, in the present invention, an optical fiber signal transmission device that converts a digital signal to an optical signal and transmits the signal through an optical fiber is combined with a GP-IB path line and a G
Interposed between the P-IB path line and the GP −
A signal direction switching circuit is provided between the IB path line and the optical fiber signal transmission device, and a transfer control circuit is provided in the handshake line of the GP-IB path line, thereby forming a standard interface bus extension device. It is characterized by

The present invention will be described in detail below using the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a standard interface bus extension device of the present invention and its connection to a GP-IB cable.

The optical fiber signal transmission devices 6 and 4 connected by a long optical fiber cable 10 convert the input digital signals into optical signals, transmit them to the other party via the optical fiber cable 10, and convert them back into digital signals. Since there is almost no signal deterioration caused by the optical fiber cable 10, these two optical fiber signal transmission devices 6.4 can be installed at a considerable distance apart.

In this invention, signal direction switching circuits 2 and 5 are connected to the optical fiber signal transmission devices 6 and 4, respectively, and a CP-IB cable 9 is connected to the signal direction switching circuits 2 and 5.

GP-IB devices 6 and 7 such as measuring instruments and computers are connected to the other end of the GP-IB cable 9, and the GP-IB cable 9 on the signal direction switching circuit 2 side is connected to
The P-IB controller 1 is connected, and in this invention, the transfer control circuit 11 is also connected. 8 is another GP-IB device connected to the GP-IB device 6 via a GP-IB cable 9.

Figure 2 shows the CP-I of the GP-IB extension device of this invention.
FIG. 3 is a detailed diagram showing the connection with the B cable 9. FIG. G in this diagram
In the P-IB cable 9, DI61 to DI8 are data lines, DAV (Data Valid).

NRFD (Not Ready'For Data
), NDAC(NotDa, ta Accepted
) is the handshake line, IFC (Interfa
ce C1ean), ATN (Attentio
n).

SRQ (5service Request), R
EN (Remote Enable), E6I (E
ndOrIdentify) indicates the management line, each of which has the functions shown in the table below.

FIG. 3 shows, for example, a signal direction switching circuit 2 for DIo 1 to 8 lines, and a terminal A connected to a pass line has a circuit connected in series with an inverter 14 and a NAND circuit 12 facing terminal B. The circuit is connected so that a signal flows from terminal C to terminal A, and the circuit is also connected so that a signal flows from terminal C to terminal A by reversing the direction of the circuit. All of the above circuits are provided for each line of the GP-IB cable 9. Of these, the cheater line, handshake line, and management line EC)I are connected to a switching circuit 2A consisting of a NOR circuit 16 and an inverter 14 shown in FIG.

In this switching circuit 2A, the two outputs of the NOR circuit 16 are connected to terminals F and G, one output is connected to terminal J, and the output of inverter 14 is connected to terminal H. The connections between these terminals H, J, and F and the terminals 1 and E of the NAND circuit 12 shown in FIG. 3 are as shown in FIG. 2, and the terminals B,
C is connected to the input and output terminals of the optical fiber signal transmission device B, respectively.

Further, the signal switching circuit 5 is provided with circuits connected to the input and output terminals of the optical fiber signal transmission device 4 for each line, and one of the circuits is provided with a buffer 15.
is interposed.

In the signal direction switching circuit configured as described above, when the terminal G in FIG.
When the level is H'', the signal is transmitted from the CP-IB machine W7 through the optical fiber cable 10 to the GP-IB equipment 6 and 8, and when the switching terminal G is at the level L, the signal is transmitted from the CP-IB machine W7 to the GP-IB equipment 6 and 8, and vice versa. It is designed to be transmitted in the direction.

Furthermore, the transfer control circuit 11, as shown in FIG.
It consists of a pulse generator 16, an inverter 17 connected to this output terminal, and two NAND circuits 18 and 19, and the output of the NAND circuit 18 is applied to the NRFD.
The outputs of the ND circuits 19 are respectively connected to NDACs. This transfer control circuit 11 is a circuit that forcibly delays the handshake time when the signal transmission speed of the optical fiber signal transmission device is slow (in the case of a device that performs parallel-to-serial conversion). That is, data transmission is made possible by making the period of pulses generated by the pulse generator 16 slower than the signal transmission speed of the optical fiber signal transmission device B.

Then, by setting the common input terminals K of the NAND circuits 18 and 19 to the l″H level, the handshake time can be forcibly delayed, and by setting the common input terminals K to the “°L” level, the handshake can be performed at the normal speed. You can do it. When performing transmission between CP and IB equipment that does not pass through the fiber signal transmission device 6, this terminal K may be set to the "L" level.

Since the CP-IB extension device of the present invention is constructed as described above, it is simpler and cheaper in construction than conventional extension devices. Also, when transmitting or receiving data, it is necessary to separately output a transmission/reception switching signal, but since many of today's controllers (computers) are equipped with DI6 output, this can be done easily. I can do it.

As explained above, the standard interface bus extension device of the present invention installs an optical fiber signal transmission device between two standard interface buses,
The signal transmission direction is switched by a signal direction switching circuit,
By converting the P-IB cable signal from parallel to serial and transmitting it using an optical fiber cable, the difference in transmission speed can be determined by using a transfer control circuit. GP-I
This has the effect of removing restrictions on the length of the B cable.

As a result, it is possible to quickly transmit signals between GP-IB devices installed at distant locations, and there is an advantage that the CP-IB devices can be effectively utilized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a standard interface bus extension device of the present invention and its connection with a GP-IB cable, FIG. 2 is a circuit configuration diagram of the standard interface bus extension device of this invention, and FIG. Figure, Figure 4, Figure 5
The figure is a circuit diagram of the main part of FIG. 2 for explaining the configuration of an interface bus extension device with the symbol f<p of the present invention. 1 ・GP-IB controller, 2, 5... Signal direction switching circuit, 6, 4 Optical fiber signal transmission device, 6゜7
．． 8・GP-IB equipment, 9...GP-IB cable, 10...optical fiber cable, 11...transfer control circuit, 12.18.19...NAND circuit, 16.
・・NOR circuit, 14° 17・Inverter, 15...
Buffer, 16... pulse generator. Agent Patent Attorney Makoto Ogawa − Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita Figure 1 H Figure 3 4 Figure 4 Figure 5

Claims (1)

[Claims] A device for extending a standard interface bus for exchanging digital signals between digital devices such as measuring instruments and computers beyond its length limit, the device being interposed between the ends of the standard interface bus, An optical fiber signal transmission device that converts a digital signal and an optical signal and transmits the signal through an optical fiber; a signal direction switching circuit that switches the transmission direction of the optical fiber signal transmission device; A standard interface bus extension device comprising a transfer control circuit that adjusts the difference in signal transmission speed between optical signals.