JPH06125261A - Input circuit - Google Patents

Input circuit

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Publication number
JPH06125261A
JPH06125261A JP4274150A JP27415092A JPH06125261A JP H06125261 A JPH06125261 A JP H06125261A JP 4274150 A JP4274150 A JP 4274150A JP 27415092 A JP27415092 A JP 27415092A JP H06125261 A JPH06125261 A JP H06125261A
Authority
JP
Japan
Prior art keywords
input
resistance
pull
control signal
signal line
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP4274150A
Other languages
Japanese (ja)
Inventor
Masaaki Abe
正顕 阿部
Original Assignee
Mitsubishi Electric Corp
三菱電機株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp, 三菱電機株式会社 filed Critical Mitsubishi Electric Corp
Priority to JP4274150A priority Critical patent/JPH06125261A/en
Publication of JPH06125261A publication Critical patent/JPH06125261A/en
Pending legal-status Critical Current

Links

Abstract

(57) [Abstract] [Purpose] An input circuit that allows the pull-up resistance value of an input signal line to be programmable by a resistance element that can be opened and closed by a control signal without having a resistance element and a switch transistor separately. To get In an input circuit having a specification in which an input signal is pulled up by a resistance, pull-up resistance values of input signal lines are set to different values by pull-up resistance elements 301 and 311 which can be opened and closed by a control signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input circuit in which the characteristics of the input circuit can be selected by programmably setting the value of an additional resistance connected to an input signal line.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional input pull-up circuit (prior art 1). In the figure, 100 is a pull-up resistor connected to an input signal, and 110 is an input for connecting the input signal to the outside. A terminal, 120 is a buffer for transmitting an input signal to an internal circuit.

Next, the operation of the input pull-up circuit shown in FIG. 6 will be described. The input signal input from the input terminal 110 is pulled up by the pull-up resistor 100. The pull-up input signal is transmitted to the internal circuit via the buffer 120. Such a pull-up resistor is usually used for the following purposes. At the timing when the bus signal line is not connected to any driver, it prevents the erroneous input (in the case of negative logic signal) due to the floating state and theoretically uncertain level. Used for pulling up the signal line when the open drain output is used. Improves noise immunity in an environment susceptible to noise.

According to the above configuration / operation, it is difficult to change the built-in resistance value set at the time of manufacturing the IC to the optimum resistance value for the corresponding system or its operating state. For example, the following cases correspond to this. For floating prevention, if the appropriate resistance range changes due to the drive capacity of the driver IC, or if the appropriate resistance range changes due to the drive capacity of the driver IC even for open drain output, the situation in which the noise environment deteriorates Then, there are cases where you want to change the resistance value.

Further, since the pull-up resistance value is added in parallel to the signal line, even when the correspondence is made outside the IC,
It is impossible to increase the effective resistance value. In other words, the IC must be redesigned / remanufactured for the change in the resistance value.

FIG. 7 shows the configuration of another conventional input pull-down circuit (prior art 2).
Is a pull-down resistor connected to the input signal, 140 is an input terminal for connecting the input signal to the outside, and 150 is a buffer for transmitting the input signal to the internal circuit.

Next, the operation of the input pull-down circuit shown in FIG. 7 will be described. The input signal input from the input terminal 140 is pulled down by the pull-down resistor 130. The pull-down input signal is transmitted to the internal circuit via the buffer 150. The pull-down resistor 130 is usually used for the following purposes. At the timing when the bus signal line is not connected to any driver, erroneous input due to a floating state and theoretically uncertain level is prevented (in the case of positive logic signal). Improves noise immunity in an environment susceptible to noise.

According to the above configuration / operation, it is difficult to change the built-in resistance value set at the time of IC manufacturing to the optimum resistance value for the corresponding system or its operating state. For example, the following cases correspond to this. In order to prevent floating, if the appropriate resistance range changes due to the drive capability of the driver IC, it may be desirable to change the resistance value when the noise environment deteriorates.

Further, since the pull-up resistance value is applied in parallel to the signal line, even when the correspondence is made outside the IC,
It is impossible to increase the effective resistance value. That is, the IC must be redesigned / remanufactured for the change in the resistance value.

FIG. 8 shows the configuration of another conventional input circuit (conventional technique 3) and shows one method for solving the above-mentioned problem in the conventional technique 1.
The method is based on the same idea as the method shown in the "programmable input circuit" disclosed in Japanese Patent No. 521. In the figure, 300 is a pull-up resistor, 310 is a pull-up resistor, 320 is a switch MOS transistor for controlling the connection between the pull-up resistor 300 and the input signal line, and 330 is for controlling the connection between the pull-up resistor 310 and the input signal line. Switch MOS transistor, 340 is a switch MO
A control signal line of the S transistor 320, 350 is a control signal line of the switching MOS transistor 330, 360 is an input terminal for connecting the input signal to the outside, and 370 is a buffer for transmitting the input signal to an internal circuit.

Next, the operation of the input circuit shown in FIG. 8 will be described. An input signal from the outside is input to the inside via the input terminal 360. When the control signal line 340 becomes LOW level, the switching MOS transistor 320 becomes O
The N state is set, and the pull-up resistor 300 is connected to the internal input signal line. Similarly, the control signal line 350 is LOW.
When in the level state, the switching MOS transistor 3
30 is turned on, and the pull-up resistor 310 is connected to the internal input signal line.

When the control signal line 340 is in the HIGH level state, the MOS transistor 320 is in the OFF state and the pull-up resistor 300 is disconnected from the internal input signal line. Similarly, when the control signal line 350 becomes the high level state, the switching MOS transistor 33
0 is turned off, and the pull-up resistor 310 is disconnected from the internal input signal line.

According to the above configuration / operation, it is possible to set the pull-up resistor 300 and the pull-up resistor 310 to the connected / unconnected state by the ON / OFF operation of the control signal lines 340 and 350. However, the above-mentioned JP-A-1
Similar to the "programmable input circuit" disclosed in Japanese Patent Laid-Open No. 91521/1982, a switch element is required in addition to the resistance element, resulting in an increase in area and cost required for realizing the function.

FIG. 9 shows the configuration of another conventional input circuit (prior art 4), and shows one method for solving the problem of the prior art 2 described above.
"Programmable input circuit" disclosed in Japanese Patent No. 1
It is based on the same idea as the method shown in. In the figure, 400 is a pull-down resistor, 410 is a pull-down resistor, 420 is a switching MOS transistor that controls the connection between the pull-down resistor 400 and the input signal line, and 430 is a switching MOS transistor that controls the connection between the pull-down resistor 410 and the input signal line. 440 is a switching MOS
A control signal line of the transistor 420, 450 is a control signal line of the switching MOS transistor 430, 460 is an input terminal for connecting the input signal to the outside, and 470 is a buffer for transmitting the input signal to an internal circuit.

Next, the operation of the input circuit shown in FIG. 9 will be described. An input signal from the outside is input to the inside via the input terminal 460. When the control signal line 440 is in the HIGH level state, the switching MOS transistor 420 is in the ON state, and the pull-down resistor 400 is connected to the internal input signal line. Similarly, the control signal line 450 is HI
In the GH level state, the switching MOS transistor 430 is turned on and the pull-down resistor 410 is connected to the internal input signal line.

When the control signal line 440 goes low, the MOS transistor 420 turns off and the pull-down resistor 400 is disconnected from the internal input signal line. Similarly, when the control signal line 450 is in the LOW level state, the switching MOS transistor 430 is in the OFF state, and the pull-down resistor 410 is disconnected from the internal input signal line.

According to the above configuration / operation, the pull-down resistors 400 and 410 can be set to the connected / unconnected state by the ON / OFF operation of the control signal lines 440 and 450. However, the above-mentioned JP-A-1
Similar to the "programmable input circuit" disclosed in Japanese Patent Laid-Open No. 91521/1982, a switch element is required in addition to the resistance element, resulting in an increase in area and cost required for realizing the function.

FIG. 10 shows a configuration of a conventional input circuit (prior art 5) having specifications including a series resistance. In the figure, 160 is an input resistance serially connected to an input signal, and 170 is an input signal and an external device. Input terminal to connect to, 18
Reference numeral 0 is a buffer for transmitting an input signal to the internal circuit.

Next, the operation of the input circuit shown in FIG. 10 will be described. The input signal input from the input terminal 170 is input to the buffer 180 via the input resistor 160. After that, it is transmitted to the internal circuit as the output of the buffer 180. The input resistor 160 is realized by a polysilicon resistor or a diffused resistor in the IC and is used for the purpose of preventing latch-up or intentionally increasing the signal delay.

According to the above configuration / operation, it is difficult to change the built-in input resistance value set at the time of manufacturing the IC. Further, since the input resistance is added in series to the signal line, it is impossible to reduce the effective resistance value even when the correspondence is made outside the IC. That is, in order to change the resistance value, the IC must be redesigned / remanufactured again.

FIG. 11 shows the structure of a conventional input circuit (prior art 6) for receiving a signal in which a transmission line is impedance matched by a terminating resistor.
Reference numerals 90 and 200 denote terminating resistors, 210 is an input terminal for connecting an input signal to the outside, 220 is a buffer for transmitting the input signal to the inside, and 230 is a transmission line for transmitting the input signal.

Next, the operation of the input circuit shown in FIG. 11 will be described. The input signal transmitted via the transmission line 230 is impedance-matched by the terminating resistor 190 and the terminating resistor 200, input from the input terminal 210, and transmitted to the internal circuit via the buffer 220.

According to such a configuration / operation, the terminating resistance for matching with the transmission line impedance is set by hardware in the operating state, and it is impossible to change the terminating resistance value in a programmable manner. .

FIG. 12 shows the configuration of another conventional input circuit (prior art 7) and shows one method for solving the problem of the prior art 6. In the figure, 60
0 is a pull-up resistor, 610 is a pull-up resistor, 620
Is a switching MOS switch for controlling the connection between the input resistor 600 and the input signal line, 630 is a switching MOS switch for controlling the connection between the input resistor 610 and the input signal line, 640 is a control signal line for the switching MOS switch 620, and 650 Is a control signal line for the switching MOS switch 630, 660 is a pull-down resistor, 670 is a pull-down resistor, 680 is a switching MOS transistor for controlling connection between the pull-down resistor 660 and the input signal line, and 690 is a pull-down resistor 6.
70 is a switching MOS transistor for controlling the connection between the input signal line 70 and the input signal line, and 770 is a switching MOS transistor 6
80 is a control signal line, 710 is a control signal line for the switching MOS transistor 690, 760 is a buffer for transmitting the input signal to the internal circuit, 770 is an input terminal for connecting the input signal to the outside, and 780 is for transmitting the input signal. It is the incoming transmission line.

Next, the operation of the input circuit shown in FIG. 12 will be described. This is a combination of the above-mentioned conventional technique 1 and conventional technique 2, in which the pull-up resistors 600 and 610 are turned on by the control signals from the control signal lines 640 and 650.
00 and 710 are intended to set the pull-down resistors programmable.

However, by adopting this structure at the end of the transmission line, the impedance matching control of the transmission line can be performed according to the characteristics of the transmission line, but the steady through current still exists as in the prior art 5. Will be done.

[0027]

According to the input circuit of the prior art 1, it is difficult to change the built-in pull-up resistance value set at the time of manufacturing the IC at the time after manufacturing the IC. That is, there has been a problem that the IC must be redesigned / remanufactured in order to change the value of the pull-up resistor incorporated in the IC once. Also, IC
Since it is connected in parallel if an additional resistance is attached externally, it is impossible to make the effective resistance value seen from the external signal line equal to or higher than the built-in pull-up resistance value. Further, there is a problem that the resistance value cannot be set to an intended value due to variations in IC manufacturing. Further, with the configuration of the input circuit according to the conventional technique 3, although it can be set programmable, both the resistor and the transistor for the changeover switch are required, the number of parts is increased, and the cost of the device itself is increased. There was a point.

According to the configuration of the input circuit according to the conventional technique 2 described above, it is difficult to change the built-in pull-down resistance value set at the time of manufacturing the IC. That is, there is a problem that the IC must be redesigned / remanufactured in order to change the value of the pull-down resistor incorporated in the IC once. Even if an additional resistance is provided outside the IC, it is impossible to make the effective pull-down resistance value seen from the external signal line more than the built-in pull-down resistance value. Further, with the configuration of the input circuit according to the prior art 4, the setting can be performed programmatically, but both the resistor and the transistor for the changeover switch are required, the number of parts is increased, and the cost of the device itself is increased. was there.

According to the configuration of the input circuit according to the prior art 5, it is difficult to change the built-in input series resistance value set at the time of manufacturing the IC. That is, there has been a problem that the IC must be redesigned / remanufactured in order to change the value of the input series resistance once incorporated in the IC. Even if an additional resistor is provided outside the IC, it is impossible to make the effective input series resistance value seen from the external signal line equal to or less than the built-in input series resistance value.

According to the configuration of the input circuit according to the conventional technique 6, the matching resistance of the transmission line is fixed according to the value of the transmission line impedance by the ordinary external resistance, and the resistance of the transmission line is fixed. Correspondingly, it is impossible to programmably set the pull-up resistance value and the pull-down resistance value.

According to the structure of the input circuit of the prior art 7, there is a problem that a steady through current exists.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to open and close an input signal line by a resistance element that can be opened / closed by a control signal without separately having a resistance element and a switching switch transistor. A first object is to obtain an input circuit that allows the pull-up resistance value to be programmable.

Further, the present invention provides an input circuit in which a pull-down resistance value of an input signal line can be set programmable by a resistance element which can be opened / closed by a control signal without separately having a resistance element and a switching switch transistor. The second purpose is to obtain.

A third object of the present invention is to obtain an input circuit capable of programmably setting the input series resistance value of the input signal line.

Further, according to the present invention, the steady through current is prevented, and the pull-up resistance value and the pull-down resistance value for the input signal can be set programmable without separately having the resistance element and the switching switch transistor. A fourth object is to obtain an input circuit.

[0036]

An input circuit according to the present invention is an input circuit having a specification in which an input signal is pulled up by a resistor, and a pull-up resistance value of an input signal line is different depending on a resistance element which can be opened / closed by a control signal. The setting means for setting the value is provided.

In the input circuit according to the present invention, the input circuit is designed to pull down the input signal with a resistor, and the pulling down resistance value of the input signal line is set to a different value by the resistance element which can be opened / closed by the control signal. Is provided.

Further, the input circuit according to the present invention is an input circuit of a specification having a series resistance in the input, and a setting means for setting the input series resistance value of the input signal line to a different value by the resistance element which can be opened and closed by the control signal. Is provided.

Further, the input circuit according to the present invention is an input circuit of a specification in which an input signal is pulled up / down by a resistor, and a pull-up resistor of an input signal line is formed by a combination of a resistance element and a capacitor element which can be opened / closed by a control signal. The setting value and the pull-down resistance value are set to different values, and a setting / prevention means for preventing a direct current passing through the pull-up resistance and the pull-down resistance is provided.

[0040]

In the input circuit according to the present invention, the pull-up resistance value of the input signal line is programmably set to a different value by the resistance element which can be opened / closed by the control signal.

Further, the pull-down resistance value of the input signal line is programmable and set to a different value by the combination of the resistance elements which can be opened and closed by the control signal.

Further, the input resistance and the delay time of the input circuit are set to different values programmable by a combination of a switch element and a resistance element which are opened and closed by a control signal, or a combination of a resistance element which is opened and closed by a control signal.

Further, the steady through current is prevented, and the pull-up resistance value and the pull-down resistance value of the input signal line are programmable to different values by the resistance element which can be opened / closed by the control signal.

[0044]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of an input circuit according to the present invention. In the figure, reference numeral 301 is a pull-up resistance element that has the functions of the pull-up resistor 300 and the switching MOS transistor 320 in the configuration shown in FIG. 8 and that can be opened / closed by a control signal. Similarly, reference numeral 311 is a pull-up resistance element that has the functions of the pull-up resistor 310 and the switch MOS transistor 330 in the configuration shown in FIG. 8 and that can be opened / closed by a control signal.

Next, the operation of the input circuit shown in FIG. 1 will be described. An input signal from the outside is input to the inside via the input terminal 360. When the control signal line 340 is in the LOW level state, the pull-up resistance element 301 that can be opened / closed by the control signal is in the ON state, and the resistance component thereof is connected to the input signal line. Similarly, the control signal line 350 is L
In the OW level state, the pull-up resistance element 311 that can be opened and closed by the control signal is turned on, and the resistance component is connected to the input signal line.

When the control signal line 340 is in the HIGH level state, the pull-up resistance element 301 which can be opened / closed by the control signal is in the OFF state and disconnected from the input signal line. Similarly, when the control signal line 350 is in the HIGH level state, the pull-up resistance element 311 which can be opened / closed by the control signal is in the OFF state and disconnected from the input signal line.

Further, in the above, the control signal line 34
Although the case where the 0 and 350 are operated digitally has been described, the resistance values of the pull-up resistance elements 301 and 311 which can be opened and closed by the control signal can be continuously changed by controlling the analog operation. is there.

[Embodiment 2] FIG. 2 is a circuit diagram showing a structure of another input circuit according to the present invention. In the figure, 40
Reference numeral 1 is a pull-down MOS transistor (pull-down resistance element) that collectively functions the pull-down resistor 400 and the switch MOS transistor 420 having the configuration shown in FIG. Similarly, 411 is a pull-down MOS transistor (pull-down resistance element) that combines the functions of the pull-down resistor 410 and the switch MOS transistor 430 shown in FIG.

Next, the operation of the input circuit shown in FIG. 2 will be described. An input signal from the outside is input to the inside via the input terminal 460. When the control signal line 440 becomes the high level state, the pull-down MOS transistor 401
Turns on, and the resistance component is connected to the input signal line. Similarly, when the control signal line 450 is in the HIGH level state, the pull-down MOS transistor 411 is
Turns on, and the resistance component is connected to the input signal line.

When the control signal line 440 is in the LOW level state, the pull-down MOS transistor 401 is in the OFF state and disconnected from the input signal line. Similarly, when the control signal line 450 is in the LOW level state,
The pull-down MOS transistor 411 is turned off and disconnected from the input signal line.

[Third Embodiment] FIG. 3 is a circuit diagram showing a structure of another input circuit according to the present invention. In the figure, 50
0 is an input resistance, 510 is an input resistance, 520 is a switching MOS switch for making the input resistance 500 short-circuited when the control signal line 540 is in the HIGH state, and 530 is an input resistance when the control signal line 500 is in the HIGH state. 510
MOS switch for switching to short circuit,
540 is a control signal line for the switching MOS switch 520,
550 is a control signal line for the switching MOS switch 530,
Reference numeral 560 is an input terminal for connecting an input signal to the outside, 570 is a buffer for transmitting the input signal to an internal circuit, and 580 is an input resistor.

Next, the operation of the input circuit shown in FIG. 3 will be described. An input signal from the outside is input to the inside via the input terminal 560 and further transmitted to the input resistor 580. When the control signal line 540 is in the HIGH level state, the switching MOS switch 520 is in the ON state, and the input resistance 5
00 is short-circuited. Similarly, the control signal line 550 is H
When in the IGH level state, the switching MOS switch 5
30 is turned on and the input resistor 510 is short-circuited. The input signal that has passed through the input resistor is buffer 57.
It is transmitted to the internal circuit via 0.

Here, the control signal line 540 and the control signal line 5
Input terminal 5 by setting HIGH / LOW level of 50
The effective input resistance value estimated from 60 can be controlled. Since the buffer 570 always has an input capacitance, the fact that the input resistance value can be controlled means that the delay time with respect to an input signal from the outside can be controlled. Furthermore, according to the present invention, it is possible to adaptively set the input resistance and the delay time by controlling the control signal line 540 and the control signal line 550 even in the operating state.

In the above explanation of the operation of FIG. 3,
Although the control signal lines 540 and 550 are operated digitally, it is possible to continuously control the resistance value and the delay time by operating the control signal lines 540 and 550 digitally.

In the present embodiment, the resistor and the switching MOS transistor described above are connected in parallel,
Although two basic units are used, one unit or three or more units may be used. Further, switching MOS transistors may be provided at both ends of the input resistor 580.

[Embodiment 4] FIG. 4 is a circuit diagram showing a structure of another input circuit according to the present invention. The input resistance 500, the input resistance 510, and the input resistance 580 shown in FIG. 3 are connected in series, but in the input circuit shown in FIG. 4, the input resistance 501, the input resistance 511, and the input resistance 511 Resistance 5
81 is changed to a parallel connection relationship. With the change of the resistance connection relation, the switching MOS transistor 5
20 and 530 are connected in series to the resistors, like switching MOS transistors 521 and 531.

Next, the operation of the input circuit shown in FIG. 4 will be described. An input signal from the outside is input to the inside via the input terminal 560. When the control signal line 540 is in the LOW level state, the switching MOS switch 521 is in the OFF state, and the signal path passing through the input resistor 501 is cut off. Similarly, when the control signal line 550 is in the LOW level state, the switching MOS switch 531 is in the OFF state, and the signal path passing through the input resistor 511 is cut off. The input signal that has passed through the input resistor is buffer 57.
It is transmitted to the inside through 0.

Here, as in the case shown in FIG. 3, the effective input resistance value and delay time estimated from the input terminal can be controlled by setting the HIGH / LOW level of the control signal line 540 and the control signal line 550. Further, similarly to the case shown in FIG. 3, if the control signals 540 and 550 are operated not only digitally but also in analog, it is possible to continuously control the resistance value and the delay time. is there.
Further, not only a combination of a switch element and a resistance element which is opened and closed by a control signal but also a resistance element which can be opened and closed by a control signal can be configured.

In this embodiment, two units are used as the basic unit in which the resistor and the switching MOS transistor are connected in series in the above-mentioned example, but one unit or three or more units may be used. Further, a switching MOS transistor may be provided in series with the input resistor 581.

In FIGS. 3 and 4, the resistance values are controlled in series or in parallel, but it is also possible to combine both. That is, by combining the basic unit in which the resistance and the switching MOS transistor are connected in series shown in FIG. 3 and the basic unit in which the resistance and the switching MOS transistor are connected in parallel shown in FIG. 4, the effective input resistance value and the input It is possible to control the delay time.

[Embodiment 5] FIG. 5 is a circuit diagram showing another structure of the input circuit according to the present invention. In the figure, 79
0 is a pull-up resistance element that can be opened and closed by a control signal,
Reference numeral 800 is a pull-up resistance element that can be opened / closed by a control signal, 810 is a pull-down resistance element that can be opened / closed by a control signal, 820 is a pull-down resistance element that can be opened / closed by a control signal, and 720 is a pull-up that can be opened / closed by a control signal. MOS for Preventing Steady Penetration Current of Resistance Element 790
The capacitor 730 is a MOS for preventing a steady through current of the pull-up resistance element 800 that can be opened / closed by a control signal.
A capacitor, 740 is a MOS for preventing a constant through current of the pull-down resistance element 810 that can be opened / closed by a control signal.
A capacitor, 750 is a MOS for preventing a constant through current of the pull-down resistance element 820 that can be opened / closed by a control signal.
A capacitor, 640 is a control signal line for a pull-up resistance element 790 that can be opened / closed by a control signal, 650 is a control signal line for a pull-up resistance element 800 that can be opened / closed by a control signal, and 700 is a pull-down for open / close by a control signal. A control signal line of the resistance element 810, a control signal line 710 of the pull-down resistance element 820 that can be opened / closed by a control signal,
Reference numeral 760 is a buffer for transmitting an input signal to an internal circuit, 77
Reference numeral 0 is an input terminal for connecting an input signal to the outside, and 780 is a transmission line for transmitting the input signal.

Next, the operation of the input circuit shown in FIG. 5 will be described. An input signal from the outside is input to the inside via the input terminal 770. When the control signal line 640 is in the LOW level state, the pull-up resistance element 790 that can be opened / closed by the control signal is in the ON state, and the resistance component is connected to the input signal line. Similarly, the control signal line 650 is L
In the OW level state, the pull-up resistance element 800 that can be opened and closed by the control signal is turned on, and the resistance component is connected to the input signal line.

When the control signal line 700 is in the HIGH level state, the pull-down resistance element 810 that can be opened / closed by the control signal is in the ON state, and the resistance component is connected to the input signal line. Similarly, when the control signal line 710 is in the HIGH level state, the pull-up resistance element 820 that can be opened and closed by the control signal is in the ON state, and the resistance component is connected to the input signal line. The MOS capacitor 720 for preventing the steady through current blocks the steady through current of the pull-up resistance element 790 which can be opened / closed by the control signal. Also, an MO for preventing steady through current
The S capacitor 730 blocks a steady through current of the pull-up resistance element 800 that can be opened / closed by a control signal. A pull-up resistance element 8 that can be opened / closed by a control signal by a MOS capacitor 740 for preventing steady through current.
Ten steady-state shoot-through currents are blocked. Further, the steady-state through-current preventing MOS capacitor 750 blocks the steady-state through-current of the pull-up resistance element 820 which can be opened / closed by a control signal.

As described above, the pull-up resistance value and the pull-down resistance value for the signal line can be set to be pull-programmable. By adopting this configuration for the transmission line, it becomes possible to flexibly cope with impedance matching by adaptively controlling the control signal according to the characteristics of the transmission line.

In the above configuration, the case where the control signal lines 640, 650, 700 and 710 are operated digitally has been described. However, the pull-down resistance element 790 which can be opened / closed by analog control. , 800,
It is also possible to continuously change the resistance values of 810 and 820.

[0066]

As described above, according to the present invention,
There is an effect that the pull-up resistor attached to the input buffer can be programmably selected without requiring both the resistance element and the switching transistor.

Further, there is an effect that the pull-down resistor attached to the input buffer can be programmably selected without requiring both the resistance element and the switching transistor.

Further, there is an effect that the input circuit delay time can be selected by programmable selection of the input series resistance attached to the input buffer.

Further, it is possible to programmably select the pull-up resistance value and the pull-down resistance value attached to the input buffer without requiring both the resistance element and the switching transistor, and to prevent the steady through current of the resistance. There is an effect that adaptive impedance matching can be performed according to the characteristics of the transmission line.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an input circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an input circuit according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an input circuit according to an embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of an input circuit according to an embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of an input circuit according to an embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a conventional input circuit (prior art 1).

FIG. 7 is a circuit diagram showing a configuration of a conventional input circuit (prior art 2).

FIG. 8 is a circuit diagram showing a configuration of a conventional input circuit (prior art 3).

FIG. 9 is a circuit diagram showing a configuration of a conventional input circuit (prior art 4).

FIG. 10 is a circuit diagram showing a configuration of a conventional input circuit (prior art 5).

FIG. 11 is a circuit diagram showing a configuration of a conventional input circuit (prior art 6).

FIG. 12 is a circuit diagram showing a configuration of a conventional input circuit (prior art 7).

[Explanation of symbols]

 301 pull-up resistance element 311 pull-up resistance element 401 pull-down resistance element 411 pull-down resistance element 500 input resistance 501 input resistance 510 input resistance 511 input resistance 520 switching MOS switch 521 switching MOS switch 530 switching MOS switch 531 Switching MOS switch 580 Input resistance 581 Input resistance 720 MOS capacitor 730 MOS capacitor 740 MOS capacitor 750 MOS capacitor 790 Pull-up resistance element 800 Pull-up resistance element 810 Pull-down resistance element 820 Pull-down resistance element

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[Procedure amendment]

[Submission date] January 27, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

Next, the operation of the input pull-up circuit shown in FIG. 6 will be described. The input signal input from the input terminal 110 is pulled up by the pull-up resistor 100 . Pull-up input signal is transmitted to the internal circuit via the buffer 120. Such a pull-up resistor is usually used for the following purposes. At the timing when the bus signal line is not connected to any driver, it prevents the erroneous input (in the case of negative logic signal) due to the floating state and theoretically uncertain level. Used for pulling up the signal line when the open drain output is used. Improves noise immunity in an environment susceptible to noise.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

Next, the operation of the input pull-down circuit shown in FIG. 7 will be described. The input signal input from the input terminal 140 is pulled down by the pull-down resistor 130 . Pull-down input signal is transmitted to the internal circuit via the buffer 150. The pull-down resistor 130 is usually used for the following purposes. At the timing when the bus signal line is not connected to any driver, erroneous input due to a floating state and theoretically uncertain level is prevented (in the case of positive logic signal). Improves noise immunity in an environment susceptible to noise.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

[Embodiment 2] FIG. 2 is a circuit diagram showing a structure of another input circuit according to the present invention. In the figure, 40
1 is a pull summarizes the function of pull-down resistor 400 and the switching MOS transistor 420 having the configuration shown in FIG. 9 <br/> down MOS transistor (pull-down resistance element). Similarly, reference numeral 411 is a pull-down MOS transistor (pull-down resistance element) in which the functions of the pull-down resistor 410 and the switch MOS transistor 430 having the configuration shown in FIG. 9 are summarized.

Claims (4)

[Claims]
1. An input circuit having a specification for pulling up an input signal with a resistor, further comprising setting means for setting a pull-up resistance value of an input signal line to a different value by a resistance element which can be opened / closed by a control signal. Input circuit to be.
2. An input circuit having a specification for pulling down an input signal with a resistance, further comprising setting means for setting a pull-down resistance value of an input signal line to a different value by a resistance element which can be opened / closed by a control signal. Input circuit.
3. An input circuit having a series resistance at the input, further comprising setting means for setting the input series resistance value of the input signal line to a different value by a resistance element which can be opened / closed by a control signal. Input circuit.
4. In an input circuit having a specification for pulling up / pulling down an input signal with a resistance, the pull-up resistance value and the pull-down resistance value of the input signal line differ depending on the combination of a resistance element and a capacitor element that can be opened / closed by a control signal. An input circuit characterized by being provided with setting / prevention means for preventing a direct current from passing through the pull-up resistor and the pull-down resistor.
JP4274150A 1992-10-13 1992-10-13 Input circuit Pending JPH06125261A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP4274150A JPH06125261A (en) 1992-10-13 1992-10-13 Input circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4274150A JPH06125261A (en) 1992-10-13 1992-10-13 Input circuit

Publications (1)

Publication Number Publication Date
JPH06125261A true JPH06125261A (en) 1994-05-06

Family

ID=17537726

Family Applications (1)

Application Number Title Priority Date Filing Date
JP4274150A Pending JPH06125261A (en) 1992-10-13 1992-10-13 Input circuit

Country Status (1)

Country Link
JP (1) JPH06125261A (en)

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