JPH05274069A - Terminating resistor circuit and terminating resistor attaching/detaching method - Google Patents

Abstract

PURPOSE:To realize storage, attachment, and detachment free from maintenance by attaching and detaching a terminating resistor by an external switch signal. CONSTITUTION:In this terminating resistor circuit, a regulator 6 provided on the side of a power line 4a is connected to a signal line 4b between computer apparatuses 1 and 2 through a terminating resistor 5. A bidirectional switching element consisting of an active element is provided in series to the terminating resistor 5 and is turned on/off by the external switch signal to attach/detach the terminating resistor 5 to/from a bus line 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to SCSI (Small).
Computer System Interfac
e) System, especially upgraded SCSI-
The present invention relates to a terminating resistor circuit for a bus line between computer devices using two systems and a method for attaching and detaching the terminating resistor.

[0002]

2. Description of the Related Art First, an interface of computer equipment will be briefly described. Conventionally, GP for automatic measurement has been used as a standard interface for small computers.
-IB, RS-232C for communication, etc. are known.
These are used by being incorporated in the host computer or optionally added to the board. The electrical specifications and execution procedures of each interface are determined according to the required functions, and the connection with the host is made up of the portions where the electrical level is the same in the bus line described later.

The interface of the SCSI specification has the same connection with the host, and the SCS is connected via the host adapter.
The I bus line is accessed. In SCSI, a device that sends a command, such as a host computer, is called an initiator, and a device that executes a command, such as a hard disk or a printer, is called a target.
However, in a SCSI system, in some cases, the initiator can be the target, and conversely, the target can be the initiator. The initiator and target are connected by a bus line called a SCSI bus. The devices on this SCSI bus are
It is called a SCSI device without distinguishing between initiator and target, but up to 8 SCSI devices can be on the SCSI bus.
The device is connectable.

Signals on the SCSI bus are configured as shown in FIG. 5 in the case of single-ended type.
In this figure, 21 is an initiator and 22 is a target. As shown in this figure, the signal of the SCSI bus is composed of a total of 18 signal lines including the upper 9 data signals (including one odd parity bit) and the lower 9 control signals. All these signals are 0, 1
Has been treated with a signal.

FIG. 6 shows an example of connection between the initiator 21 and the target 22. What is shown in this figure is generally an SCS.
I's single-ended type. As shown in this figure, the initiator 21 and the target 22 are connected by a SCSI bus line 23.
In this figure, 24a is a power supply line to which 5V is normally applied. Reference numeral 24b is the signal line shown in FIG. 5, and although only one line is shown, there are actually 18 lines. Reference numeral 24c is an earth line, and there are actually a plurality of earth lines. This power line 24a, signal line 24b,
The earth line 24c is collectively called a bus line. 25 is a terminating resistor (terminator), which is
Impedance matching with the bus line cable is required to transfer 0 and 1 signals between the SCSI devices such as the initiator 21 and the target 22 as an accurate rectangular wave, and it is necessary to provide each at the end SCSI device. Is. In the SCSI system, this terminating resistor 25 needs to be provided with the number of signal lines, that is, 18 sets, for each device, and the resistance value of the circuit of FIG.
5b is defined as 330Ω.

However, the characteristic impedance of the signal line 24b is generally 110Ω, but the terminating resistor 25 has a total of 132Ω in the above example, and since the respective impedances are different, the impedance of the bus line cable is missed. It has the drawback that matching is likely to occur, and the cable length cannot be made very long, and the signal transfer speed must be suppressed to some extent.

Therefore, the upgraded SCSI-2 has been developed in order to improve the above-mentioned inconvenience. An example thereof is shown in FIG. In this figure, the same reference numerals as those in FIG. 6 indicate the same members, so detailed description thereof will be omitted.
Only the differences will be described. In this figure, 25c is a terminating resistor connected to the signal line 24b side, and its resistance value is 110Ω. Reference numeral 26 is a regulator connected to the power supply line 24a side, which is normally 5V of the power supply line 24a.
It is for adjusting the voltage to 2.85V and supplying a constant voltage to the terminating resistor 25c. The terminating resistor 25c and the regulator 26 are connected in series. Reference numeral 27 is a capacitor provided between the regulator 26 and the ground line 24c for removing noise and ripple on the power supply line 24a and on the output side of the regulator 27.

Next, FIG. 8 shows a configuration example of a SCSI system. In this figure, 22a, 22b, 22c, 22
d is a target of a CD-ROM device, an optical disk device, a scanner, a printer, or the like. If multiple SCSI devices (targets 22) are connected as shown in this figure, the SCS
Devices (in this case, targets 22a, 22b, 2) connected between the devices (initiator 21, target 22d in this case) connected to the I bus
The terminating resistor of 2c) must be removed. Conventionally, the following two methods are conceivable for attaching or detaching the terminating resistor. The target 22 of FIG. 7 is replaced by the targets 22a and 2 of FIG.
In the case of 2b and 22c, a mechanical switch such as a DIP switch is provided at the position A, and the switch is turned on and off. Termination resistance (between A and A'when the target 22 of FIG. 7 is the targets 22a, 22b, and 22c of FIG. 8)
By attaching and detaching the connector with built-in connector or the resistor module to the device.

[0009]

However, in the method of (1), the number of contact points of the switch is equal to the number of signal lines (see FIG. 7).
(18 in the case of the above example), and it is necessary to switch the plurality of switches one by one. The method (1) requires maintenance such that the connector with built-in resistor and the resistor module are stored in the form of accessories, which may cause a problem such as loss of the connector or module.
Also, artificially installing this connector or module,
There is also the inconvenience of requiring maintenance for removal. For example, in a SCSI system, up to eight devices can be connected, but in recent situations where multiple devices must be connected in a complicated manner, the above connectors and modules are frequently attached and detached. This must be done, and this maintenance will be a major obstacle when changing the system.

The present invention has been made in view of the above problems, and enables termination resistors to be attached / detached by an external switch signal, thereby realizing maintenance-free storage, attachment, and detachment. It is an object of the present invention to provide a method for attaching and detaching a circuit and a terminating resistor.

[0011]

In order to achieve the above object, the termination resistance circuit of the present invention is connected to a signal line between computer devices with a regulator provided on the power supply line side through the termination resistance. In the termination resistor circuit,
A bidirectional switching element including an active element is provided in series with the terminating resistor. Further, the method of attaching and detaching the terminating resistor of the present invention is characterized in that, in the terminating resistor circuit, the terminating resistor is attached to and detached from the bus line by turning on and off the bidirectional switching element by an external switch signal. The termination resistance circuit of the present invention is characterized in that, in the termination resistance circuit, a switching element made of an active element is provided between the power supply line and the regulator. Further, according to the method of attaching and detaching the terminating resistor of the present invention, the bidirectional switching element and the switching element are turned on by an external switch signal in the terminating resistor circuit in which the switching element composed of the active element is provided between the power supply line and the regulator. Is turned off to simultaneously attach / detach the regulator to / from the bus line and detach / attach the terminating resistor.

[0012]

As described above, in the termination resistance circuit of the present invention, since the bidirectional switching element composed of the active element is provided in series with the termination resistance between the signal line and the regulator,
For example, when a low level ON signal is input from the outside, even if the signal level from the signal line is higher or lower than the level of the voltage output from the regulator, the regulator operates from the signal line that constitutes the bidirectional switching element. A terminating resistor is attached to the bus line because either the switching element in the direction in which current flows to the switch or the switching element in the direction in which current flows from the regulator to the signal line turns on (that is, the bidirectional switching element turns on). It will be in a state of being stuck. When a high-level off signal is input from the outside, the bidirectional switching element is turned off, and the terminating resistor is removed from the bus line. Therefore, the terminating resistor can be attached or detached by an external switch signal. Therefore, by incorporating the bidirectional switching element in the device, there is no need to perform maintenance such as storage, attachment, and removal of the resistor built-in connector and the resistor module.

Further, in the above terminating resistor circuit, when a switching element composed of an active element is provided between the power supply line and the regulator, when the bidirectional switching element is on, the power supply line and the regulator are connected. When the switching element is turned on and the bidirectional switching element is turned off, the switching element between the power supply line and the regulator is turned off, and the regulator and the terminating resistor are attached / detached to / from the bus line at the same time. become. Therefore, when the bidirectional switching element is off, that is, when the terminating resistor is removed from the bus line, current does not flow from the power supply line to the regulator. It becomes possible to use electricity.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an example of connection of computer equipment. This figure is an example of connection of a system compatible with SCSI-2 and is called a single-ended TYPE. Reference numeral 1 is an initiator, 2 is a target such as a CD-ROM device, and 3 is a SCSI bus line for connecting the initiator 1 and the target 2. For the bus line 3, a cable with a connector having 50 terminals or 68 terminals is used. A power line 4a, a signal line 4b, and a ground line 4c pass through the bus line 3. Normally, 5V is applied to the power supply line 4a through one line. Signal line 4b
5 shows only one line as shown in FIG. 5, but actually there are 18 signal lines as shown in FIG. There are actually a plurality of earth lines 4c. The power supply line 4a, the signal line 4b, and the earth line 4c are collectively called a bus line.

Reference numeral 5 denotes a terminating resistor (terminator) connected to the signal line 4b, which is a bus for transferring 0 and 1 signals between SCSI devices such as the initiator 1 and the target 2 as an accurate rectangular wave. This is for matching the impedance with the cable, and is required to be provided in each SCSI device such as the initiator 1 and the target 2 at the end. This terminating resistor 5 is a single-ended TYPE circuit,
It is necessary to provide the number of signal lines 4b for each device, that is, 18 and the resistance value thereof is 110Ω. Reference numeral 6 denotes a regulator connected to the power supply line 4a side for adjusting the normal 5V voltage of the power supply line 4a to 2.85V and supplying a constant voltage to the terminating resistor 5. The terminating resistor 5 and the regulator 6 are connected in series. Reference numeral 7 is a capacitor provided between the regulator 6 and the ground line 4c for removing noise and ripple on the power supply line 4a and on the output side of the regulator 6.

In order to attach / detach the terminating resistor 5 to / from the bus line 3 in this terminating resistor circuit, in the present embodiment, a plurality of bidirectional switchings made of active elements are provided between the terminating resistor 5 and the regulator 6, that is, at the point B. Although elements (not shown) are provided, the number of terminating resistors 5 needs to be provided corresponding to the number of signal lines 4b, so that the number of switching elements corresponding thereto is also provided. Here, the terminating resistor 5, the regulator 6, the capacitor 7 and the like which compose the terminating resistor circuit are integrated together with the bidirectional switching element.

FIG. 2 is an equivalent circuit diagram of an integrated termination resistance circuit including a bidirectional switching element. C in this figure
The points D, E correspond to the points C, D, E in FIG. In this figure, reference numeral 8 denotes a plurality of bidirectional switching elements provided between the terminating resistor 5 and the regulator 6, which is composed of a PNP type transistor.
Reference numeral 9 is a bias resistor for applying a bias to the bidirectional switching element 8 and 10 (a portion surrounded by a dotted line).
Is a switching element and a transistor with a built-in resistor. The switching element 10 functions as a switch for turning on / off the bidirectional switching element according to an external signal. Although only nine terminating resistors 5 are shown in this drawing for simplification of the drawing, actually, the number of signal lines, that is, eighteen, is required.

The operation when the circuit shown in FIG. 2 is connected to the bus line of the SCSI system will be described.
Now, when a low level ON signal is input from the point F (the switch connected to the point F and the ground is closed), the signal level from the signal line 4b is higher than the voltage level output from the regulator 6 or Even if it is low, either one of the switching element 8a in the direction in which the current flows from the signal line 4b to the regulator 6 or the switching element 8b in the direction in which the current flows from the regulator 6 to the signal line 4b is turned on (that is, Since the bidirectional switching element 8 is turned on), the terminating resistor 5
Is attached to the bus line 3. When a high-level off signal is input from the outside (the switch connected to the F point and the ground is opened), the bidirectional switching element 8 is turned off and the terminating resistor 5 is removed from the bus line 3. It will be in a state where it was opened. Therefore, the terminating resistor 5 can be attached or detached by an external switch signal. The integrated circuit shown in this figure is preferably manufactured using hybrid IC technology, but it goes without saying that it may be manufactured using other technologies such as monolithic IC technology.

FIG. 3 is an equivalent circuit diagram of a termination resistance circuit of another embodiment. 2 is different from FIG. 2 in that a switching element 11 such as a resistor built-in transistor (a portion surrounded by a dotted line) is provided between the power supply line 4a and the regulator 6 in FIG. That is.
The switching element 11 is operated by the switching element 10, and when the switching element 10 is turned on, the switching element 11 is also turned on.
When 0 is off, the switching element 11 is also off.
In this way, the terminating resistor 5 can be attached / detached simultaneously with the attachment / detachment of the regulator 6.

FIG. 4 is a schematic view of the outside when a plurality of targets 2a, 2b, 2c, 2d are attached to the target 2 of FIG. The initiator 1 and the targets 2a, 2b, 2c, 2d shown in this figure incorporate the termination resistance circuit shown in FIG. 2 or FIG. 2 and 3
In the termination resistance circuit shown in (1), since the number of termination resistors 5 is 9, it is necessary to incorporate two termination resistance circuits in the device. In FIG. 4, 12, 13a, 13
b, 13c, 13d are changeover switches attached to the outside for inputting a signal to point F in FIG. 2, for example. As shown in this figure, a plurality of targets 2a,
When attaching 2b, 2c, and 2d, for example, the switches 12 and 13d are turned on, and the switches 13a and 13b,
The terminating resistor 5 of the intermediate targets 2a, 2b, 2c can be easily attached and detached by simply turning off 13c. Further, in the case of the circuit of FIG. 3, the terminating resistor 5 and the regulator 6 are simultaneously attached and detached.

The termination resistance circuits shown in FIGS. 2 and 3 are merely examples, and any termination resistance circuit may be used as long as the intended purpose can be achieved. For example, in these drawings, the bidirectional switching element 8, the switching element 10, and the switching element 11 of FIG. 3 may use other ICs instead of the transistors. Further, the switching element 10 is not always necessary. Further, the positions where the terminating resistor 5 and the bidirectional switching element 8 are provided are not limited to the embodiment, and the point is that the terminating resistor 5 and the bidirectional switching element 8 are provided between the signal line 4b and the regulator 6. It suffices if a series circuit of is provided. Therefore, the bidirectional switching element 8 may be provided between the terminating resistor 5 and the signal line 4b. Further, in the termination resistance circuits of FIGS. 2 and 3, nine termination resistors 5 are provided, but the number of termination resistors 5 in one termination resistance circuit is not limited to the above. Furthermore, the switches 12, 13a, 13 shown in FIG.
b, 13c, and 13d are not limited to those of this embodiment, and the on / off operation of this switch may be electronically performed by software or the like.

[0022]

In the termination resistance circuit of the present invention, since the termination resistance and the bidirectional switching element are provided between the signal line and the regulator, the bidirectional switching element is turned on / off by an external switch signal. As a result, the terminating resistor can be attached and detached. Therefore,
By incorporating the bidirectional switching element in the device, there is no need to perform maintenance such as storage, installation, and removal of the resistor built-in connector and the resistor module. Further, when the switching element is provided between the regulator and the power supply line, power saving can be achieved as compared with the case where only the bidirectional switching element is provided. Further, if a plurality of terminating resistors and bidirectional switching elements are integrated by using hybrid IC technology or the like, mounting on a device such as SCSI becomes easy.

[Brief description of drawings]

FIG. 1 is an internal connection diagram for explaining a connection example of a computer device to which the present invention is applied.

FIG. 2 is an equivalent circuit diagram of a termination resistance circuit for implementing the present invention.

FIG. 3 is an equivalent circuit diagram of another termination resistance circuit for implementing the present invention.

FIG. 4 is an external schematic diagram of a connection example of a computer device to which the present invention is applied.

FIG. 5 is a schematic diagram of signals on a SCSI bus.

FIG. 6 is an internal connection diagram for explaining a connection example of a conventional computer device.

FIG. 7 is an internal connection diagram for explaining a connection example of a conventional computer device.

FIG. 8 is an external schematic diagram of a connection example of a conventional computer device.

[Explanation of symbols]

 1 Target 2 Initiator 3 Bus Line 4a Power Line 4b Signal Line 4c Earth Line 5 Termination Resistor 6 Regulator 7 Capacitor 8 Bidirectional Switching Element 9 Bias Resistor 10 Switching Element 11 Switching Element 12 Switch 13a Switch 13b Switch 13c Switch 13d Switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Yasuda Murata Manufacturing Co., Ltd. 2 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Prefecture

Claims (4)

[Claims] 1. A termination in which a regulator (6) provided on the power supply line (4a) side is connected to a signal line (4b) between computer equipment (1) and (2) through a terminating resistor (5). A terminating resistance circuit, characterized in that a bidirectional switching element (8) consisting of an active element is provided in series with the terminating resistance (5) in the resistance circuit. 2. A method of attaching / detaching a terminating resistor in a terminating resistor circuit according to claim 1, wherein the bidirectional switching element (8) is turned on / off by an external switch signal to terminate the bus line (3). A method of attaching and detaching a terminating resistor, characterized in that the resistor (5) is attached and detached. 3. The termination resistance circuit according to claim 1, further comprising a switching element (11) formed of an active element between the power supply line (4a) and the regulator (6). 4. A method of attaching and detaching a terminating resistor in a terminating resistor circuit according to claim 3, wherein the bidirectional switching element (8) and the switching element (11) are turned on and off by an external switch signal, A method of attaching and detaching a terminating resistor, characterized in that the terminating resistor (5) is attached and detached at the same time when the regulator (6) is attached to and detached from the line (3).