Sharp R-21JCA-F service manual Touch Control Panel Assembly, Description of LSI

R-21JCA-F

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL

Control Unit

Control unit consists of LSI, power source circuit, synchroniz- ing signal circuit, reset circuit, buzzer circuit, encoder circuit and indicator circuit.

1)LSI

This LSI controls the encoder signal, relay driving signal for oven function, buzzer signal and LED signal.

2)Power Source Circuit

This circuit generates voltage necessary in the control unit.

4)Reset Circuit

A circuit to generate a signals which resets the LSI to the initial state when power is supplied.

5)Buzzer Circuit

The buzzer is responsive to signals from the LSI to emit audible sounds (completion sound).

6)Door Sensing Switch

A switch to “tell” the LSI if the door is open or closed.

Symbol	Voltage	Application
VC	+5V (*)	LSI(I-1)
VR	+20V (*)	RELAY(RY1, RY2)

(*)The voltage under the condition when all LEDs light up. The voltage VR will vary according to the quantity of the LEDs which light up.

3)Synchronizing Signal Circuit

The power source synchronizing signal is available in order to compose a basic standard time in the clock circuit. It accompanies a very small error because it works on commercial frequency.

7)Relay Circuit

To drive the magnetron, fan motor, antenna motor and light the oven lamp.

8)Encoder

The encoder generates the pulse signal, and the pulse signal is sent to the LSI.

9)Indicator Circuit

Indicator elements are the Light-emitting diodes (LD1- LD20).

This circuit consists of 4-digits and 5 segments.

DESCRIPTION OF LSI

LSI

The I/O signal of the LSI is detailed in the following table.

Pin No.	Signal	I/O	Description
1	D3	OUT	Segment data signal.
			Signal is input to the cathodes of the light-emitting diodes (LD1, LD6, LD11 and LD16).
2	D4	OUT	Digit selection signal.
			Signal is input to the anodes of the light-emitting diodes (LD16 - LD20).
3	D5	OUT	Digit selection signal.
			Signal is input to the anodes of the light-emitting diodes (LD11 - LD15).
4	D6	OUT	Digit selection signal.
			Signal is input to the anodes of the light-emitting diodes (LD6 - LD10).
5	D7	OUT	Digit selection signal.
			Signal is input to the anodes of the light-emitting diodes (LD1 - LD5).
6	P20	IN	Connected to VDD terminal.
7	P21	IN	Connected to VSS terminal.
8	P22	IN	Signal coming from encoder.
			When the encoder is turned, the contacts of encoder make pulse signals. And pulse
			signals are input into P22.

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