JPS63209218A - Bidirectional interface circuit - Google Patents

Abstract

PURPOSE:To convert data from the logical level of a certain level to other logical level with bidirectionality by connecting the titled circuit with plural integrated circuits each different in power source potential, and setting in output terminal at an I/O control terminal. CONSTITUTION:A low voltage type output circuit 108 is turned off and a high voltage type output circuit 107 is turned on. The data of a low potential level inputted from an I/O terminal 102 are converted through a level shifter due to an inverter G4, P-type FETs Q3 and Q5 and N-type FETs Q4 and Q5 to a P-type FETG1 and a high voltage type voltage amplitude and given through gates G1 and G2 to a P-type FETG1 and an N-type FETQ2. The data are outputted from these FETQ1 and Q2 to an I/O terminal 101 as the data of the high voltage type. When the high voltage type data are converted to low voltage type data, an 'H' level signal is set to an I/O control terminal 103. Thus, the low voltage type output circuit 108 is turned on, the high voltage type output circuit 107 is turned off and as the result, the flow of the data is converted reversely, inputted and outputted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an interface circuit, and particularly to an interface circuit that bidirectionally transfers data between multiple integrated circuits driven by different power sources by using a voltage conversion circuit. Regarding.

[Conventional technology]

Conventionally, this type of interface circuit combines two I10 terminals as shown in FIG. 3, receives data from the I10 terminal indicated by 302 using the I10 control terminal 303, and outputs the data from the I10 terminal indicated by 301. Alternatively, the user could select whether to use 301 as an input terminal and output data from 302. In addition, 3
01°302.303 and the logic level of the integrated circuit are the same.

By stacking these in several stages, as shown in Fig. 4, 401.
The microcomputer's RO
There are conventional techniques such as M, used for interfacing RAM and data buses.

[Problem that the invention attempts to solve]

The conventional interface circuit described above makes the logic level of its own circuit the same as the logic level of the integrated circuit, switches I10 using a control signal, and exchanges data between multiple integrated circuits, so it is difficult to use different power supplies. A drawback is that it is impossible to transfer data bidirectionally between multiple integrated circuits.

[Means for solving problems]

The interface circuit of the present invention is an integrated circuit that drives an I10 terminal that inputs and outputs at a high voltage logic level and an I10 terminal that inputs and outputs an input and output at a low voltage logic level with a smaller amplitude depending on the logic level. connected and converted to a different voltage logic level via a level shifter,
■/○ Has the ability to select the output terminal using the control terminal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. 1
01 is an integrated circuit with a certain power supply system, and I and 10 terminals are used for receiving and passing data.

102 is an integrated circuit having a power supply system lower than that of 101, and an I10 terminal which receives and transfers data. 104 is 101
105 is a terminal to which the same power supply potential as the integrated circuit connected to 102 is applied. 106 is a ground. 103 is an I10 control terminal. Note that, in order to enable an interface between integrated circuits of the same voltage system, and considering productivity, it is desirable that each circuit have the same withstand voltage characteristics.

An example of an interface is a low power system (e.g. 3V system)
The operation up to connecting the integrated circuit and the I10 terminal 102 and outputting the input data to the I10 terminal 101 connected to the integrated circuit of a high power supply system (for example, 5V system) will be described. In this case, the I10 terminal 101 is set as the OUT terminal, and in order to output the data input from the I10 terminal 102, the I10 control terminal 103 is set to a low level (hereinafter referred to as "'L").
’)) Set the level.

The L'' level signal set to the I10 control terminal 103 is input to the NOR gate G6 via the NAND gate E and the inverter G7, and
, P-type FET by the output of NOR gate G6
Q7 and N-type FET Q8 are turned off, and the data that is input to the NAND gate G1 via the NOR gate G2 and inverter G3 and input to the other input terminals of each of Gt and Gz is passed. That is, the low voltage output circuit 108 is turned off and the high voltage output circuit 107 is turned on. The low potential level data input from the I10 terminal 102 is input to the inverter-5=G4, P-type FET Q3. G5 and N-type FET Q4.
It is converted into a voltage amplitude of a high voltage system through a level shifter by G6, and E T'G 1. P type FE for output via G2
TG, and N-type FETQ2, and these FETs
I10 terminal 10 as high voltage system data from Ql, G2
Output to 1.

When converting high voltage system data to low voltage system data,
By setting a "H" level signal to the I10 control terminal 103, the low voltage system output circuit 108 is turned ON and the high voltage system output circuit 107 is turned OFF, and as a result, the data flow is converted in the opposite manner as described above. input and output.

FIG. 2 is a circuit diagram showing a second embodiment. 206 is the ground, and 204 is the same power supply potential as the integrated circuit connected to 201. This is an interface circuit that has a common high potential side, and functions as opposed to the first embodiment, which has a common low potential side. This is exactly the same as the first embodiment.

〔Effect of the invention〕

As explained above, the present invention connects multiple integrated circuits with different power supply potentials to the interface circuit of the present invention and sets the output terminal using the I10 control terminal, thereby achieving a certain logic level. It has the effect of bidirectionally converting data to other logical levels.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a second embodiment of the present invention, FIG. 3 is a diagram showing an example of a conventional interface circuit, and FIG. The figure is a block diagram in which conventional interface circuits are stacked to transfer data from multiple integrated circuits in both directions. 101.201 is the I10 terminal with the high voltage integrated circuit, 1
02, 202 is ■10 terminal with low voltage integrated circuit, 10
3, 203 is a control terminal, 104 is a high voltage system +
side power supply terminal, 105 is the + side power supply terminal of the low voltage system, 106
, 206 is the ground level, 107.207 is the high voltage output circuit, 108.208 is the low voltage output circuit, 1
09° 209 is a level shifter, 204 is a high voltage system one side power supply terminal, and 205 is a low voltage system one side power supply terminal.

Claims (1)

[Claims] In a bidirectional interface circuit that interfaces between multiple integrated circuits, the output is connected to a first input/output terminal that inputs or outputs to a first voltage amplitude system integrated circuit, and level-converted data is input from the outside. The output is connected to a first output circuit that outputs according to an input control signal, and a second input/output terminal that inputs or outputs to an integrated circuit of a second voltage amplitude system lower than the first voltage system. a second output circuit that outputs data input from the first input/output terminal in accordance with the control signal; and a second output circuit that outputs data input from the second voltage amplitude system integrated circuit connected to the second input/output terminal. and a level shifter that performs level conversion and inputs the level to the first output circuit, and switches the output states of the first and second output circuits according to the control signal to provide a logical interface between different voltage system integrated circuits. bidirectional interface circuit.