JPH02146653A - Interface circuit - Google Patents

Abstract

PURPOSE:To eliminate the influence of noises to the transmission signal and to prevent the occurrence of malfunctions in a simple constitution by setting the input/output ports in the output states with an active function block and then in the input states with an inactive function block respectively. CONSTITUTION:The input/output port I/O1 - I/Om are allocated to the function blocks 2 - 4 as the ports of a microcomputer 1 to output the control signals. These input/output ports are set in the output states with active blocks 2 - 4 and then in the input states with inactive blocks 2 - 4 respectively. At the same time, the output ports O1 - Oe of the microcomputer 1 are connected to the input ports of blocks 2 - 4 via the switching means Tgammax1 - Tgammaxl which are turned on only with the active blocks 2 - 4. Thus the control signal is surely transmitted when the blocks 2 - 4 are kept active with no occurrence of malfunctions. Then the disturbance of noises can be avoided to the peripheral circuits and devices when the blocks 2 - 4 are inactive.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a microcomputer (hereinafter referred to as MICO27, -
.

This application relates to an interface circuit used to control functional blocks using a 3D interface (abbreviated as ``controller'').

BACKGROUND OF THE INVENTION In recent years, interference with peripheral circuits and equipment due to noise made up of the reference oscillation of microcomputers and its harmonics has become a problem. Conventionally, countermeasures to such problems have been taken by inserting a filter in combination with a choke coil and a capacitor into the wiring connecting the microcomputer and the functional blocks.

Problems to be Solved by the Invention However, in the conventional configuration described above, each filter has a unique frequency band, and to deal with broadband noise, it is necessary to use a plurality of filters, or the filter may not be able to control the transmitted signal. This poses a problem in that it is necessary to take this into consideration since there is a risk of distortion resulting in malfunction.

The present invention has been developed in view of the above-mentioned problems, and has the following three effects: preventing noise radiation and leakage over a wide band, and has a simple configuration that reduces the influence on transmitted signals. The present invention provides an interface circuit that does not cause malfunctions.

Means for Solving the Problems - 1 - In order to solve the problem, the ink face circuit of the present invention uses the input/output ports as ports of the microcomputer that outputs control signals to the functional blocks, and outputs control signals to the functional blocks. The block is configured to change to an output state when it operates, and to an input state when it does not operate.

Furthermore, the output port 1 of the microcomputer is connected to the input port of the functional block via a 1-run sister that is turned on only when the functional block operates.

According to the above-described configuration, the present invention separates the input/output ports or output ports of the microcomputer that outputs control signals to the functional blocks with high impedance when the functional blocks are not in operation, and the wiring connected thereto. This prevents the radiation and outflow of noise from the microcomputer's reference oscillation or its high frequency from the wiring and functional blocks.
When the function block is operating, the above ports and wiring are as follows.
Connected without impedance, control signals can be transmitted reliably, and malfunctions will not occur.

Embodiments Hereinafter, interface circuits of embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an interface circuit in an embodiment of the present invention. In FIG. 1, 1 is a microcomputer, 2 is a compact disk (hereinafter abbreviated as CD) block, 3 is a tuner block, and 4 is a tape recorder block, each of which is controlled by the microcomputer 1. K.O.
1~Kop is the key matrix output port of the microcontroller, K
11~KI.

is the key matrix input port of the microcomputer, and both constitute the key matrix. S is a key matrix switch group, which selects a functional block or selects the operation of each functional block. Among them, S11 is a CD selection switch 5 switch, S12 is a tuner selection switch, and S21 is a key matrix switch group. are tape recorder selection switches, and each functional block is selected by these switches.

5 is a CD selection signal output terminal, and a CD selection switch S
11 is pressed, the output of this CD selection signal output terminal 5 changes from L (low level/I/) to H (high level).

01 to 0 flood (hereinafter referred to collectively as O only) are the two output ports on the microcomputer 1, 01 is the output port of the acceptance number, and engineering 101 to engineering/○m (in the generic terminology, engineering/○
) are m input/output ports of microcontroller 1, Ilo
, is the j-th input/output port, 11 to In (indicated by ■ if called a) are the n input ports of microcomputer 1,
Ik is the second input capo-1-. Also, ■CD
o~ICD℃+. is (1+fi+m) of CD block 2
n input ports, ○cD1~0CDn'', CD plug 2 (7) n output ports, Trxo~Trxf
i is a transistor, and Rb0 to Rb1-Rb are resistors. The keytrix output port KO1 of the microcomputer 1 is connected to the input port IcD0 of the CD block 2 via the emitter and collector of the transistor Trx06, and the output port KO1 of the microcomputer 1 is
are connected to the CD cover lCD1 to IC1]2 via the emitters and collectors of the transistors TrX1 to TrxR, and further, the base of the transistor Trx is connected to the CD selection signal output terminal 6 via the resistor Rb. Therefore, when the CD selection switch S11 is pressed and the CD selection signal output terminal 5 becomes H, a current flows to the base of the transistor IX via the resistor Rb, and the transistor Trx
turns on, and key matrix output ports KO1 and C
From D output bottom ○, CD block input port lCD1~
The control signal is transferred to the engineering CDR. Ilo is connected to the input capo of CD block 2 "CDR+1-" and is connected to the microcomputer 1 input/output capo.
0 input capo) I is the output capo of CD block 2 - 1-0CD
connected to.

6 is the power input terminal of CD block 2, 7 is its power supply, T
rl and Tr2 are transistors, R1 and R2 are resistors, the power supply 7 is connected to the CD block power input terminal 6 via the emitter and collector of transistor Tr1, and the base of transistor Tr1 is connected to resistor R. The emitter of the transistor Tr2 is grounded, and the emitter of the transistor Tr2 is connected to the collector of the transistor Tr2 through the transistor Tr2.
The base of is connected to the CD block selection signal output terminal of the microcomputer 1 via a resistor R2. Therefore, only when the CD selection switch S11 is pressed and the CD block selection signal output terminal 6 becomes H, a current flows to the base of the transistor Tr2 via the resistor R2, and the l-ranta star T
r2 turns ON, and current flows through the base of transistor Tr1 via resistor R1 and transistor Tr2, transistor Tr1 turns ON, and CD block 2
A power supply 7 is supplied to the power input terminal 6 of the CD block 2.
is in the operating state.

The operation of the interface circuit configured as described above will be explained below with reference to FIGS. 1, 2, 3, and 4.

The case where each functional block is selected will be explained with reference to the flowchart in FIG. First, when the CD selection switch S11 is pressed, the process moves from step 11 to step 12, and the CD selection signal output terminal 5 is set to H, so that the transistor Tr1 is turned on as described above.
The power supply 7 is supplied to the power input terminal 6 of the CD block 2, the transistor IX is turned on, and the control signal from the microcomputer 1 is transmitted to the CD block 2. Further, in step 13, the microcomputer input/output port 1-Ilo is set to the output state, and the data is transferred from the microcomputer input/output port I10 to the CD block input port IcD. A control signal is transmitted to D←1. Further, the data signal from the CD block 2 is transmitted from the CD block output port OcD to the microcomputer input port E, and with the above, the CD block 2 becomes operational.

Further, if the tuner selection switch S12 or the tape recorder selection switch S21 is pressed, step 11
The process then proceeds to step 14 or step 15, and further proceeds to step 16, where the CD selection signal output terminal 6 is set to L, the power supply is no longer supplied to the CD block 29, and the unit becomes inoperable. The lantern star Tx is turned off. Therefore, the output port ○ of microcomputer 1 and the key matrix output port -1-
The connection from KO2 is isolated at high impedance by the transistor Trx. And this state is the second
In the figure, the microcomputer input/output port ○ is set to the input state (step 17), and the microcomputer output port ○ is set to L (step 18).

Next, FIG. 3 shows the circuit configuration inside the microcomputer of the input/output capo-1-Ilo of the microcomputer 1, and shows the circuit configuration inside the microcomputer of the input/output capo-1-Ilo.
r4 is a FET, and 10 is an input cover sofa. When set to the output state, a control signal is output by FETs Tr3 and Tr4, and when set to the input state, FETs Tr3 and Tr4 are set to OFF, and the microcomputer The input/output capo-1-Ilo is connected to the input buffer 10.

Next, FIG. 4 shows the circuit configuration inside the microcomputer of the output ports 1-0 of the microcomputer 1 and the key matrix output ports KO1 to Kop, and Tr6 and 10...-2.
- Tr6 is an FET, and a control signal is output by FETs T5 and Tr6. When microcomputer output bottom 0 is set to L, FET 6 is OFF, FET Tr
6 is set to ON.

In Figure 3, the power supply VCC and ground ■ of the microcomputer 1
ss is a location where the level of noise consisting of the reference oscillation of the microcomputer 1 or its harmonics is extremely high, and by setting the microcomputer input/output port I10 to the input state while the CD block is in the non-operating state, ■cc or (2) With the high impedance of SS, it is possible to prevent noise radiation and outflow from the wiring that is separated from the microcomputer input/output port I10 and connected to the microcomputer input/output port Ilo.

Further, in FIG. 4, when the CD block 2 is in the non-operating state, the FET Tr 6 is turned on, and noise consisting of the reference oscillation of the microcomputer 1 or its harmonics flows out to the microcomputer output port ○ via the FET Tr 6. However, the l-ranta stars TrX1 to Trxj2 in FIG. 1 are placed near the microcomputer output port ○, and the C
By turning OFF the D block 2 into a non-operating state, the wiring connected to the microcomputer output port O is separated from the microcomputer output port O, and noise radiation and outflow from the wiring can be prevented.

Further, the key matrix output capo-1-KO1 is always in an operating state, and the transistor Trx0 is arranged near the key matrix output capo-1-KO2 in a manner similar to the above, and when the CD block 2 is in an inactive state, Transistor TrX
By setting o to OF and F, the wire connected to ○1 to the key matrix output port is the key matrix output port K.
It is separated from o1, and noise radiation and outflow from the wiring can be prevented.

As described above, according to this embodiment, as the output port of the microcomputer 1 that outputs the control signal to the CD block 2, the input/output port of the microcomputer 1 that can be reassigned is assigned to the microcomputer input/output capo (Ilo), When the CD block 2 is operating, the microcomputer input/output port 1-Ilo is set to the output state, and when the CD block 2 is not operating, the microcomputer input/output port E/○ is set to the input state.
Microcomputer output boat O to which no traffic port is assigned
Alternatively, the key matrix output port Ko1 and the CD block input port CDo-IC that are shared with the key matrix
Dfl is turned ON when CD block 2 is in operation, and C
Transistor T that is OFF when D block 2 is not operating
By connecting via rx, when the CD block 2 is not operating, the microcomputer input/output port I10, the microcomputer output port ○ and the key, and the matrix output port Ko1
, CD block input port ICDo~”CDfl+
Wiring to m and CD block 2 to which the wiring connects
It is possible to prevent the reference oscillation of the microcomputer 1 and its high frequency from being radiated and leaked, and it is possible to prevent interference with peripheral equipment or interference with the tuner block 2 when it is in operation. When the CD block 2 is in operation, the microcomputer input/output port Ilo, the microcomputer output port O, the key matrix output port 1-KOl, and the CD block input ports CDo to IC0a+.

Since it is connected reliably without impedance, there is no possibility of malfunction.

13 F1/ Effects of the Invention As described above, the present invention uses input/output ports as ports of a microcomputer to output control signals to functional blocks.
If the functional block is working, it is set to the output state, and if it is not working, it is set to the input state. It is configured to be connected to the input port of the above-mentioned functional block via the ON switching means, and when the functional block is operating, the control signal is reliably transmitted and the non-functional block is connected without causing malfunction. During operation, the radiation and outflow of noise consisting of the microcomputer's reference oscillation or its harmonics from the wiring and functional blocks connected to the input/output ports and output ports of the microcomputer is prevented, and the noise caused by the above noise is prevented from radiating and outflowing from the wiring and functional blocks connected to the microcomputer's input/output ports and output ports, and prevents the noise from surrounding circuits and peripheral devices. This is an extremely effective invention.

[Brief explanation of the drawing]

FIG. 1 shows an interface 14 in an embodiment of the present invention.
\-. Figure 2 is a flowchart of the microcomputer, Figure 3 is the internal circuit diagram of the microcomputer input/output port, and Figure 4 is the microcomputer output port and scheme. FIG. 1...Microcomputer, 2...
CD block, 3... Tuner block, 4.
...Tape recorder block, 6...C
D selection signal output terminal, 01~02...Microcomputer output port, 101~l10m...Microcomputer input/output port, IcDo~Eng CDfi+rrl...
・・CD block input port, KO1~KOp ・・
...Key matrix output port, S11...
CD selection switch, S12...Tuner selection switch, S21...Tape recorder selection switch. Name of agent: Patent attorney Shigetaka Awano and one other person Figure ss

Claims (2)

[Claims] (1) A microcomputer is equipped with an input/output port assigned to a port that outputs a control signal to a functional block, and when the functional block is operating, the port is set to an output state, and when the functional block is not operating, the above port is set to the output state. An interface circuit characterized in that it is configured to set an output port to an input state. (2) A switching means is provided between the output port of the microcomputer that outputs a control signal to the functional block and the input port of the functional block, and the switching means is turned ON only when the functional block is in operation. An interface circuit characterized by comprising: