JPH0316445A - Termination system - Google Patents

Abstract

PURPOSE:To avoid a trouble by manual operation by allowing each package to detects whether or not it is located at a remotest position and validating a pull-up resistor when the package is located at the remotest position. CONSTITUTION:When a voltage at a tap tz of a voltage divider is larger than a reference voltage VR, a comparator COMP causes an output, a relay Ry closes its contact to connect the resistor R to a power supply +V. Thus, the signal line l and the bus B are subjected to pull-up. The higher voltage of the tap tz takes place only when the said package is located at the remotest position. Then each package itself detects whether it is mounted to the terminating point or not, the pull-up resistor is validated when the package is mounted at the termination point, and the pull-up resistor is invalidated when the package is not mounted at the termination point and only one pull-up resistor is realized automatically at the remotest point.

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding the termination method of a system in which signals are supplied to many packages via bus connection, each package detects whether it is the fastest or not, and if it is the farthest, a pull-up resistor is enabled. In order to eliminate the disadvantages of the conventional method by making a voltage divider having a first tap connected to the front-stage package and a second tap connected to the rear-stage package when the voltage is high; and means for connecting the pull-up resistor to the power supply when the voltage at the second tap is high. When the package is in the final stage, the pull-up resistor is connected to the power supply and pulls up the signal line, and when it is not the final stage, the pull-up resistor is disconnected from the power supply, making it the same as not having it. .

[Application fields of industrial technology]

The present invention relates to a system for terminating a system in which signals are supplied to a large number of pancages via a bus connection.

Recently, with the rapid development of microcomputers, microcomputers are increasingly being used for monitoring systems of devices. At this time, a method is generally used in which commands are sent from a package equipped with a microcontroller to each monitored package via a bus connection, and responses are returned from each package. The microcontroller E also detects whether each package is installed or not, displays it, and reports it to the host. The interface between packages is generally TTL.

When interfacing packages with TTL, it is desirable to insert a pull-up resistor at the receiving end to prevent malfunctions, and in cases where a large number of packages are connected via a bus, it is desirable to insert a pull-up resistor at the receiving end farthest from the transmitting end. Preferably pull up.

[Conventional technology]

FIG. 4 shows the monitoring system wiring section of a shelf that accommodates a large number of packages. PKC,,,PKG2,...
is the bankage, OB is the output buffer of the monitoring microcontroller,
B is a bus. Surveillance type hippopotamus sofa I of each package
B,, I BZ. . . . is connected to bus B, and the input buffer connected to bus B at the farthest position from output buffer OB In this example, a pull-up resistor R is connected to the input terminal of IBi.

Each input bath sofa I B,, I B! A pull-up resistor may be provided at the input terminal of the output buffer OB, but in this case, it is necessary to increase the driving ability of the output buffer OB, so normally there is only one pull-up resistor. Connect at the farthest point.

[Problem to be solved by the invention]

However, when monitoring a low-speed channel board of a multiplex converter, the channel board is fully installed.
The fact that this device is only partially implemented depends on the configuration of the system that uses the device, and therefore, the problem is how to pull the bus B/input buffer IB at the farthest point. It is extremely troublesome for an operator to visually determine the farthest input bus sofa and enable the pull-up resistor there, especially when there are a large number of packages. Also, if you install a pull-up resistor at the input end of every input bus sofa,
This is a problem in terms of the driving ability of the output huffer OB.

The present invention aims to improve this point, and eliminates the drawbacks of the conventional method by detecting whether each package is the farthest or not, and if it is the farthest, enabling the pull-up resistor. This is the purpose.

[Means for Solving the Problems] As shown in FIG. 1, in the present invention, the pull-up resistor R of the input buffer IB of the package is connected to the power source 1 through the contact of the relay R. 1 is a signal line connected to bus B in FIG.

The package is also provided with a voltage divider and comparator COMP which are connected in series with resistors RZ+Rl+Rz, and relays R and comparator CO? Driven by IP output. R1 is sufficiently larger than R2. Tap t1 of the voltage divider is connected to tap t2 of the voltage divider of the front package, and tap L2 is connected to tap 1. of the voltage divider of the rear package. connected to. This connection state is shown in FIG.

This connection is made by inserting the package (printed board) into the shelf. If you don't insert the package, it will be in a through state. For example, package PKG
．． is not inserted, the connection point P, is short-circuited to the connection point P2.

[Effect]

In this configuration, the voltage at tap t2 of the voltage divider is the reference value V,
If greater than I, comparator COMP produces an output and relay R
, closes the contacts and connects the resistor R to the power supply +■. This causes the signal [1 bus B1 to be pulled up. tap t
If the voltage at V,2 is lower than the reference value V,l, the comparator COMP produces no output and the relay R, is not driven and has its contacts open, so that no pull-up occurs.

Tap t! The voltage is higher than the reference value ■ only when the package in question is the farthest away. That is, each package PKC;
．． , PKG,, etc. are connected as shown in Figure 2 in the order of proximity from the output bus sofa OB in Figure 4, so tap 2 of the voltage divider of a package in the next stage is connected to the next one. The output voltage is lower than the reference value because it is dropped to the ground by the low resistance R2 in the stage, and there is no next stage, only the tap L2 of the voltage divider in the final bunkage, which is not dropped to the ground by the low resistance R2, so the output voltage is lower than the reference value. Voltage is higher than standard value. The reference value VR is set in this way.

As shown in FIG. 2(b), if the resistor R1 is sufficiently larger than the resistor R2, the tap t of the voltage divider of a package in the next stage
The voltage at tap L2 of the voltage divider in the final package is nearly V/2.

Therefore, the reference value may be set to about 3V/4.

In this way, in the present invention, each package detects whether it is mounted at the final end or not, and if it is mounted at the final end, the pull-up resistor is enabled, and if it is not the final end, the pull-up resistor is disabled. Only one pull-up resistor at the final end can be automatically realized.

Even if you remove the package that has been inserted and set,
The above state is maintained. For example, when package PKG2 is removed, connection point P+ is short-circuited to connection point P2, so it is the same as in the case of 3 packages, and the farthest bankage PKG.
A pull-up is performed. Package PKC. The furthest package is PKG. and this tap t. The output voltage of z rises and a pull-up is performed on the PKG:+.

[Embodiment] Fig. 3 shows an embodiment of the present invention, where BWB is the back wiring board of the shelf, PL is the printed circuit board of the package, and 10.12 is a connector, and the electrical connection between the BWB and the PC is through this connector 10.12. It takes place through 12. The board BWB has a pair of locking metal fittings 14.1 that form a contact point.
6, printed board Pt. is inserted between these fittings 14 and 16 while fitting the connectors 10 and 12 together.

1718 is a locking metal fitting for another pudding +ffl.

When the printed temporary PT is inserted between the metal fittings 14 and 16 as shown in FIG. 3(b), the electrical connection between them is broken, and the corresponding electrical connection is instead inserted between them as shown in FIG. 3(d). A printed circuit board voltage divider will be inserted.

When the printed board PL is removed, it will look like Figure 3 (C).
The metal fittings 14 and 16 are in contact, that is, electrically short-circuited.

The arrow in FIG. 3(d) indicates that the short-circuited metal fittings 14 and 16 are broken open by inserting the printed board. The metal fittings l4 and 16.17 and 18 are the connection points PI+PZ+... in Figure 1.
It corresponds to...

The relay Ry shown in FIG. 1 may be an electronic relay such as a transistor in addition to a mechanical relay.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to automatically pull up the signal line and therefore the bus at the farthest package, which is extremely effective without the hassle of thousands of steps.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a circuit diagram showing the connection state of a voltage divider, Fig. 3 is an explanatory diagram of an embodiment of the present invention, and Fig. 4 is an explanatory diagram of the package monitoring system wiring. It is. In Figure 1, l is a signal line connected to the bus, R is a pull-up resistor, +■ is a power supply, R. ,R,,R. is a voltage divider, LI+j
2 is its tap, COMP is a comparator, and Ry is a relay.

Claims (1)

[Claims] 1. In a system termination method in which signals are supplied to a plurality of packages through a bus connection, each package is provided with a pull-up resistor (R) for the signal line (l).
and a voltage divider (R_
2, R_1, R_2) and a means (COMP,
When the package is in the final stage, the pull-up resistor is connected to the power supply and pulls up the signal line, and when it is not the final stage, the pull-up resistor is disconnected from the power supply, making it the same as not having it. A termination method featuring: