2 Inputoutput Signal Switch Circuit

The I/O signal switch circuit selects signals (video and audio ) entered and feeds them to later stages and each output terminal. Fig. 7-2 shows the switching section of the audio/video signal switch circuit.

2-1. Audio/Video Signal Switch Circuit

The signal switching for the audio/video signal entered is carried out by Q200 SW IC (TA1218N). Each I/O signal is connected to Q200 as shown in Fig. 7-2. Each I/O control is entirely carried out through I2C bus.

2-2. Input Signals

2-2-1. Composite Video Signal

The composite video signal is input to pin 10. When the composite video signal is selected, the composite video signal is output from pin 42 and supplied to Y/C separation circuit. The signal processed by Y/C separation circuit is input to pins 30 and 32 again, finally re-selected, and then output from pins 34 and 36.

The Y/C signals input from S terminal are input to pins 12 and 14 respectively.

The video signal sent from the camera section is supplied as Y/C signal and input to pins 16 and 18. The video signal finally selected is output from pins 34 (C) and 36 (Y) respectively and supplied to the signal processing section in the later stage. At the same time, the same video signal as the finally selected video signal is output from pin 42 as a composite video signal. And then, the signal is output from the video output terminal through a buffer.

2-2-4. Audio Signal

The audio signal contains two kinds of input signals, video signal system and RGB signals. Each signal is corresponding to L and R stereo input signal system. The audio signal for video signal is selected simultaneously when the composite video signal, S (Y/C) signal and camera signal are selected.

The audio signal for RGB signal system is selected when RGB signals are selected. The audio signals output from speakers after amplified through the amplifier section in the later stage are output from pins 35 (Rout 1) and 37 (Lout 1).

On the other hand, the audio signals output from the audio output terminals are output from pins 2 (Rout 2) and 1 (Lout 2). The signal selection method is the same as the audio signals fed to the speakers. The internal block diagram of Q200 SW IC (TA1218N) is shown in Fig. 7-2.

Q200 TA1218N

VIDEO AUDIO

12 S

10 V

RGB AUDIO

Y IN

Y IN

C IN

CAMERA-Y -CAMERA-C -

VIDEO OUT

AUDIO OUT

TO AUDIO

From

Microcomputer

TO AUDIO

From

Microcomputer

Fig. 7-2 Audio/video signal switch section

PIP Non applied : 42Pin i-PIP applied : [ ] terminals are deleted

Det select

Det in

V1 in

10

V2 m

28

TV in

C1 in C2 in

Sync out

PIP Non applied : 42Pin i-PIP applied : [ ] terminals are deleted

Det select

Det in

C1 in C2 in

Sync out

V out 1

R out TV

R out 1

Fig. 7-3 Internal block diagram of TA1218N

LS1

in

11

LS2

in

15

LV1

in

8

LV2

in

29

LTV

in

V out 1

SCL SDA Address I/O 1(3 value) I/O 2(3 value) [I/O 3] [O 4]

R out TV

R out 1

Fig. 7-3 Internal block diagram of TA1218N

0 0

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