JP3089803B2 - Terminating resistor circuit and attaching / detaching method of terminating resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a SCSI (Small)
Computer System Interface
e) systems, especially upgraded SCSI-
The present invention relates to a terminating resistor circuit of a bus line between computer devices using two systems and a method of attaching and detaching a terminating resistor.

[0002]

2. Description of the Related Art First, an interface of a computer device will be briefly described. Conventionally, GP for automatic measurement has been used as a standard interface for small computers.
-IB, RS-232C for communication, and the like are known.
These are used in a form incorporated in a host computer or optionally attached to a board. The electrical specifications and execution procedures of each interface are determined by its required functions, and the connection to the host is made up of bus lines, which will be described later, that have the same electrical level.

The interface of the SCSI specification has the same connection to the host, and the SCSI interface is connected via the host adapter.
It accesses the I bus line. In SCSI, a device that sends commands, such as a host computer, is called an initiator, and a device that executes commands, such as a hard disk or a printer, is called a target.
However, in the SCSI system, in some cases, the initiator is the target, and conversely, the target is allowed to be the initiator. The initiator and the 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 distinction between initiator and target, but up to eight SCSI devices are on the SCSI bus.
Device is connectable.

The signal of the SCSI bus is configured as shown in FIG. 5 in the case of the single-ended type.
In this figure, 21 is an initiator and 22 is a target. As shown in this figure, the SCSI bus signal is composed of 18 signal lines including the upper 9 data signals (including one odd parity bit) and the lower 9 control signals. These signals are all 0, 1,
Treated by signals.

FIG. 6 shows an example of the connection between the initiator 21 and the target 22. The one shown in this figure is generally SCS
This is called I 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, reference numeral 24a denotes a power supply line to which 5 V is normally applied. Reference numeral 24b denotes the signal line shown in FIG. 5, and although only one line is shown, there are actually 18 lines. Reference numeral 24c denotes an earth line, which actually has a plurality of lines. The power supply line 24a, the signal line 24b,
The ground line 24c is collectively called a bus line. 25 is a terminating resistor (terminator), which is
In order to transfer the 0 and 1 signals between the SCSI devices such as the initiator 21 and the target 22 as an accurate rectangular wave, it is necessary to match the impedance with the bus line cable, and it is necessary to provide each of the end SCSI devices. It is. In the SCSI system, the terminating resistor 25 must be provided with the number of signal lines for each device, that is, 18 sets. The resistance value is the case 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 is 132Ω in total in the above example. Since the respective impedances are different, the impedance of the signal line 24b is different from that of the bus line cable. There is a drawback that matching tends to occur, so that the length of the cable cannot be made too long, and the signal transfer speed must be suppressed to some extent.

[0007] In order to solve the above-mentioned inconvenience, a version of SCSI-2 has been developed. An example is shown in FIG. In this figure, the same reference numerals as those in FIG. 6 indicate the same members, and thus detailed description is omitted.
Only the differences will be described. In this figure, reference numeral 25c denotes a terminating resistor connected to the signal line 24b, and its resistance value is 110Ω. Reference numeral 26 denotes a regulator connected to the side of the power supply line 24a.
This 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 denotes a capacitor provided between the vicinity of the regulator 26 and the ground line 24c, for removing noise and ripple on the power supply line 24a and 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 such as a CD-ROM device, an optical disk device, a scanner, and a printer. When a plurality of SCSI devices (targets 22) are connected as shown in FIG.
Devices connected between the devices (initiator 21 and target 22d in this case) connected to the I bus (targets 22a, 22b, 2
The terminating resistor in 2c) must be removed. Conventionally, the following two methods can be considered for attaching or removing the terminating resistor. The target 22 shown in 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. Terminating resistor (when the target 22 in FIG. 7 is the targets 22a, 22b, and 22c in FIG. 8, between A and A ')
This is done by attaching and detaching a connector with a built-in or a resistor module to and from the device.

[0009]

However, in this method, the number of switch contacts is determined by the number of signal lines (FIG. 7).
18 in the case of the above example), and it is necessary to switch the plurality of switches one by one. Further, in the method (1), maintenance for storing the connector with a built-in resistor and the resistor module in the form of an accessory is necessary, and a problem such as loss of the connector or the module can be considered.
Also, artificially installing this connector or module,
There is also a disadvantage that maintenance for removal is required. For example, in a SCSI system, a maximum of eight devices can be connected. However, in a recent situation in which a plurality of devices must be connected in a complicated manner, the above-mentioned connectors and modules are frequently attached and detached. This maintenance would be a major hindrance when rearranging the system.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a terminal resistor capable of attaching / detaching a terminal resistor by an external switch signal and realizing maintenance-free storage, installation, and removal. An object of the present invention is to provide a method for attaching and detaching a circuit and a terminating resistor.

[0011]

According to the present invention, in order to achieve the above object, a regulator provided on a power supply line side is connected to a signal line between computer devices via a terminating resistor. In the termination resistor circuit,
A bidirectional switching element comprising an active element is provided in series with the terminating resistor. Further, the method of attaching / detaching a terminating resistor according to the present invention is characterized in that in the terminating resistor circuit, a bidirectional switching element is turned on / off by an external switch signal, thereby attaching / detaching the terminating resistor to / from a bus line. Further, the termination resistor circuit according to the present invention is characterized in that, in the termination resistor circuit, a switching element including an active element is provided between the power supply line and the regulator. Further, in the method of attaching / detaching a terminating resistor according to the present invention, in the terminating resistor circuit provided with a switching element composed of an active element between the power supply line and the regulator, the bidirectional switching element and the switching element are turned on by an external switch signal. By turning off, the terminating resistor is attached and detached at the same time as attaching and detaching the regulator to and from the bus line.

[0012]

As described above, the terminating resistor circuit of the present invention is provided with a bidirectional switching element comprising an active element in series with the terminating resistor 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 signal line constituting the bidirectional switching element Either the switching element in the direction in which current flows to the switching element or the switching element in the direction in which current flows from the regulator to the signal line turns on (ie, the bidirectional switching element turns on). State. 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 termination resistor can be attached and detached by an external switch signal. Therefore, by incorporating the bidirectional switching element into the device, it is not necessary to perform maintenance of storage, installation, and removal of the resistor built-in connector and the resistor module.

Further, in the above-mentioned termination 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 connection between the power supply line and the regulator is provided. When the switching element is also 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 attachment / detachment of the regulator and the termination resistor to / from the bus line are performed simultaneously. become. Therefore, when the bidirectional switching element is off, that is, when the terminating resistor is removed from the bus line, no current flows from the power supply line to the regulator, so that the power consumption is reduced as compared with the case where only the bidirectional switching element is provided. Power can be used.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a connection example of computer equipment. This diagram is a connection example of a SCSI-2 compatible system, and is called a single-ended type. Reference numeral 1 denotes an initiator, 2 denotes a target such as a CD-ROM device, and 3 denotes a SCSI bus line connecting the initiator 1 and the target 2. For the bus line 3, a cable with a connector having 50 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, 5 V is applied to the power supply line 4a through one line. Signal line 4b
Is shown in FIG. 5 and only one line is shown. However, there are actually 18 signal lines as shown in FIG. There are actually a plurality of ground lines 4c. The power supply line 4a, the signal line 4b, and the ground 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 the 0 and 1 signals between the 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 must be provided in SCSI devices 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 signal lines, and its resistance value is 110Ω. Reference numeral 6 denotes a regulator connected to the power supply line 4a 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 denotes a capacitor provided between the vicinity of the regulator 6 and the ground line 4c for removing noise and ripple on the power supply line 4a and the output side of the regulator 6.

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

FIG. 2 is an equivalent circuit diagram of an integrated termination resistor circuit including a bidirectional switching element. C in this figure
Points D, D, and E correspond to points C, D, and 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 are constituted by PNP transistors.
Reference numeral 9 denotes 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 built-in resistor type transistor. The switching element 10 functions as a switch for turning on and off the bidirectional switching element by an external signal. Although only nine terminating resistors 5 are shown in this figure for simplification of the drawing, the number of signal lines, that is, 18, is actually required.

The operation when the circuit shown in FIG. 2 is connected to a bus line of a SCSI system will be described.
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 or lower than the voltage level output from the regulator 6. Even if it is low, either the switching element 8a in the direction in which current flows from the signal line 4b to the regulator 6 or the switching element 8b in the direction in which current flows from the regulator 6 to the signal line 4b is turned on (ie, Since the bidirectional switching element 8 is turned on), the terminal resistance 5
Is attached to the bus line 3. When a high-level off signal is input from outside (the switch connected to the point F 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 lost. Therefore, the terminal resistor 5 can be attached and detached by an external switch signal. Although the integrated circuit shown in this figure is desirably manufactured using hybrid IC technology, 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 resistor circuit according to another embodiment. 2 is different from FIG. 2 in point D ′ in FIG. 1, that is, a switching element 11 such as a transistor with a built-in resistor (a portion surrounded by a dotted line) is provided between the power supply line 4 a and the regulator 6. That is.
The switching element 11 is operated by the switching element 10. 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 termination resistor 5 can be attached and detached simultaneously with the attachment and detachment of the regulator 6.

FIG. 4 is a schematic view of the outside when a plurality of targets 2a, 2b, 2c and 2d are mounted on the target 2 of FIG. In the initiator 1 and the targets 2a, 2b, 2c, and 2d shown in this figure, the terminating resistor circuit shown in FIG. 2 or 3 is built. FIG. 2, FIG.
Since the number of the terminating resistors 5 is nine in the terminating resistor circuit shown in (1), it is necessary to incorporate two terminating resistor circuits in the device. In FIG. 4, 12, 13a, 13
b, 13c and 13d are externally mounted changeover switches 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, 2d, for example, the switches 12, 13d are turned on, and the switches 13a, 13b,
By simply turning off 13c, the terminating resistor 5 of the intermediate target 2a, 2b, 2c can be easily attached and detached. In the case of the circuit of FIG. 3, the terminating resistor 5 and the regulator 6 are simultaneously attached and detached.

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

[0022]

In the terminating resistor circuit of the present invention, since the terminating resistor and the bidirectional switching element are provided between the signal line and the regulator, the bidirectional switching element is turned on and off by an external switch signal. This makes it possible to attach and detach the terminating resistor. Therefore,
By incorporating the bidirectional switching element in the device, it is not necessary to perform storage, installation and removal maintenance of the resistor built-in connector and the resistor module. Further, when a switching element is provided between the regulator and the power supply line, power can be saved as compared with a case where only a bidirectional switching element is provided. Further, if a plurality of terminating resistors and bidirectional switching elements are integrated by using a hybrid IC technology or the like, attachment to a device such as SCSI becomes easy.

[Brief description of the drawings]

FIG. 1 is an internal connection diagram for explaining a connection example of computer equipment 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 resistor 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 SCSI bus signals.

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]

 DESCRIPTION OF SYMBOLS 1 Target 2 Initiator 3 Bus line 4a Power supply line 4b Signal line 4c Earth line 5 Terminating resistor 6 Regulator 7 Capacitor 8 Bidirectional switching element 9 Bias resistance 10 Switching element 11 Switching element 12 Switch 13a Switch 13b switch 13c switch 13d switch

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-114133 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 3/00

Claims (4)

(57) [Claims] 1. A termination in which a regulator (6) provided on a power supply line (4a) side is connected to a signal line (4b) between the computer devices (1) and (2) via a termination resistor (5). A terminating resistor circuit comprising a resistor circuit and a bidirectional switching element (8) comprising an active element provided in series with the terminating resistor (5). 2. A method for attaching and detaching a terminating resistor in a terminating resistor circuit according to claim 1, wherein the bidirectional switching element (8) is turned on and off by an external switch signal, thereby terminating the bus line (3). A method of attaching / detaching a terminating resistor, comprising attaching / detaching a resistor (5). 3. The terminating resistance circuit according to claim 1, further comprising a switching element (11) comprising an active element provided between the power supply line (4a) and the regulator (6). 4. A method 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 / detaching a terminating resistor, wherein the terminating resistor (5) is attached / detached simultaneously with attachment / detachment of a regulator (6) to / from a line (3).