JPH0475120A - Universal interface circuit - Google Patents

Abstract

PURPOSE:To connect a personal computer to external equipment by utilizing an interface of RS232C standard by using the output line and input line of the interface of RS232C standard, two photocouplers, and a fixed resistor. CONSTITUTION:This circuit is formed by using three, first to third output lines and one input line provided at the interface 1 of RS232 standard, the two photocouplers PC1, PC2 provided for input and output, and the fixed resistors R1, R2. A voltage of +PV is supplied to the first output line, and the voltage of +PV or -PV to the second output line selectively, and the voltage of -PV to the third output line by the personal computer, and it is read whether the voltage of the input line is of +PV or -PV by the personal computer. In such a way, no out-fitted power source is required, and also, the interface of RS232C standard is connected to the external equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a general-purpose interface circuit for generalizing an RS232C standard interface installed in a personal computer (hereinafter referred to as a personal computer).

[Prior art] When trying to control external equipment with a personal computer, it is common to use an input/output expansion interface port, or in cases where at most one input/output bit is sufficient (in such cases However, if the above-mentioned input/output expansion interface board is used, the unit cost per bit becomes extremely high, making it uneconomical.

On the other hand, personal computers are usually equipped with an RS232C standard+7) interface as standard, and some of the output lines and input lines of this interface may be used for controlling external equipment.

[Problem to be solved by the invention] However, the interface of this RS232C standard,
The signal voltage level is special at 112V/+12V, so it cannot be connected to external equipment as is.

Therefore, it may be possible to insert an IC for level conversion, but this would require an external power supply for the IC, which would eventually complicate the device and increase costs.

The present invention has been made in consideration of the above circumstances, and aims to provide a general-purpose interface circuit that does not require an external power supply and can connect an RS232C standard interface and external equipment at low cost. .

[Means for Solving the Problems] The general-purpose interface circuit of the present invention is for generalizing the RS232C standard interface equipped in a computer, and includes first to third interfaces provided in the RS232C standard interface.
Using three output lines and one input line, two photocouplers provided for input and output, and a fixed resistor, the fixed resistor is connected between the first output line and the input line. Connect both terminals of the light emitting element of the input photocoupler as input terminals for connection with external equipment, connect one terminal of the light receiving element of the photocoupler to the input line of the RS232C standard interface, and connect the other terminal to the input line of the RS232C standard interface. is connected to the third output line, and both terminals of the light receiving element of the photocoupler for output are used as output terminals for connection with external equipment, and one terminal of the light emitting element of the photocoupler is connected to the second output line. and the other terminal is connected to the third output line, and the personal computer supplies +PV voltage to the first output line and 10P or - to the second output line.
The device is characterized in that the voltage of PV is selectively supplied, the voltage of -PV is supplied to the third output line, and the personal computer reads whether the voltage of the input line is +P■ or -PV. .

[Operation] When connecting the above interface circuit to an external device, the input terminal of the input photocoupler and the output terminal of the output photocoupler are respectively connected to the external device.

Thereby, the light emitting element of the input photocoupler is turned on/off in response to a signal from the external device.

When the light is off, the light receiving element is in the OFF state.

At this time, the voltage +PV of the first output line is applied to the input line of the RS232C standard interface via a fixed resistor. Also, when the light emitting element is in the lighting state, the light receiving element is also in the ON state, and the input line is connected to the third
The voltage -pv of the output line is manually input. Therefore, signals from external equipment are input to the personal computer via the photocoupler.

On the other hand, regarding the output, when the second output line is set to 10 PV/or -PV, the light emitting element of the output photocoupler turns on/off. Then, depending on the state of the light-emitting element, the light-receiving element is turned ON/OFF, and therefore, by controlling the voltage of the second output line with the personal computer, external equipment can be controlled.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

In the attached diagram, 1 is an RS232C standard interface equipped on the personal combinator;
S is the output terminal for transmission request (first output line), DR is the input terminal (input line) for data set ready, SD is the output terminal for transmission data (second output line), ER is data terminal ready. This is the output terminal (third output line) for

The RSm child is fixed at +12Vi according to a command from the personal computer. In addition, D
The voltage at the R terminal (+1.2V or -12V) is read. Further, the SD terminal is selectively set to +12V or -12V by the personal computer. Furthermore, the ER terminal is fixed at -12V by a command from a personal computer.

Then, the above four terminals RS, DRSSDSER, and 2
two photocouplers pct, pc2 and two fixed resistors R
1 and R2 constitute the general-purpose interface circuit of the embodiment.

That is, a fixed resistor R1 is connected between the RS terminal and the DR terminal. Diode of photocoupler PCI for human power (
The anode and cathode of the light-emitting device DI are used as input terminals for connection with external equipment, and the transistor (
The collector of the light receiving element Tri is connected to the DR terminal, and the emitter of the transistor Tr1 is connected to the ER terminal.

Furthermore, regarding the output photocoupler PC2, the collector and emitter of the transistor (light receiving element) Tr2 are used as output terminals for connection with external equipment, and the anode of the diode (light emitting element) D2 is connected to the fixed resistor R2 for current declaration. The cathode of the same diode D2 is connected to the SD terminal through the ER terminal.
Each is connected to m children.

When connecting the interface circuit configured in this manner to an external device, the anode and cathode of the diode D1 of the input photocoupler PCI are connected to the control signal output terminal of the external device. Further, the collector and emitter of the transistor Tr2 of the output photocoupler PC2 are connected to a control signal input terminal of an external device.

As a result, the input photocoupler P can be
The diode D1 of CI is turned on/off. When the light is off, the transistor Tr1 is in the OFF state. At this time, the voltage of the RS terminal +12V is applied to the DR terminal of the RS232C standard interface via the fixed resistor R1.
is input.

Furthermore, when the diode D1 is in the lit state, the transistor Tri is in the ON state, and the voltage of the ER terminal -12V is input to the DRAW child via the transistor Trl. Therefore, the signal from the external device is connected to the photocoupler PCI.
It will be manually input to the DR terminal via the DR terminal.

On the other hand, regarding the output, when the SD terminal is set to +12V/- or -12V, the diode D2 of the output photocoupler PC2 turns on/off.

Then, depending on the state of the diode D2, the transistor T
r2 is ON/or 0FFL, so D on the computer
External equipment can be controlled by controlling the voltage at the R terminal.

In this interface circuit, the signal voltage level on the external device side is the diode D1 of the input photocoupler PCI,
As long as the transistor Tr2 of the output photocoupler PC2 is within the respective specifications, it can be applied to a wide range of applications. Then, it is possible to exchange signals between the RS232C standard interface and external equipment having different signal voltage levels.

[Effects of the Invention] As described above, according to the general-purpose interface circuit of the present invention, a personal computer and an external device can be connected using an interface of the RS232C standard.

Furthermore, this interface circuit does not require a special external power supply and is composed only of a photocoupler and a fixed resistor, so it is simple in structure and inexpensive. Furthermore, when this interface circuit is used, the personal computer and external equipment are completely electrically isolated by the photocoupler, making it difficult for noise to enter the signal line.

Furthermore, this interface circuit can be configured very small and can also be mounted within the RS232C connector, thereby providing advantages such as not requiring extra space.

[Brief explanation of the drawing]

The accompanying drawing is a circuit diagram of one embodiment of the present invention. 1-RS 232 C standard interface PCI/
Input photocoupler P C2, --output photocoupler D1. D2 ・Diode (light emitting element) Trl, Tr
2...Transistor (light receiving element) R1, R2.
Fixed resistance RS...First output terminal DR...Input terminal SD...Second output terminal ER...Third output terminal

Claims (1)

[Claims] RS232C installed in a personal computer
An interface circuit for generalizing the standard interface, which includes first to third circuits provided in the RS232C standard interface.
Using three output lines and one input line, two photocouplers provided for input and output, and a fixed resistor, the fixed resistor is connected between the first output line and the input line. Connect both terminals of the light emitting element of the input photocoupler as input terminals for connection with external equipment, connect one terminal of the light receiving element of the photocoupler to the input line of the RS232C standard interface, and connect the other terminal to the input line of the RS232C standard interface. is connected to the third output line, and both terminals of the light receiving element of the photocoupler for output are used as output terminals for connection with external equipment, and one terminal of the light emitting element of the photocoupler is connected to the second output line. and the other terminal is connected to the third output line, and the personal computer supplies the voltage of +PV to the first output line, and the voltage of +PV or - to the second output line.
PV voltage is selectively supplied, a -PV voltage is supplied to a third output line, and a personal computer reads whether the voltage of the input line is +PV or -PV. interface circuit.