Toshiba TW40F80 manual Operation of Channel Selection Circuit

SECTION III: CHANNEL SELECTION CIRCUIT

1. OUTLINE OF CHANNEL SELECTION CIRCUIT SYSTEM

The channel selection circuit in the N5SS chassis employs a bus system which performs a central control by connect- ing a channel selection microcomputer to a control IC in each circuit block through control lines called a bus. In the bus system which controls each IC, the I2C bus system (two line bus system) developed by Philips Co. Ltd. in the Neth- erlands has been employed.

The ICs controlled by the I2C bus system are: IC for V/C/D signal processing (Q501), IC for A/V switching (QV01), IC for non volatile memory (QA02), Main and sub U/V tuners (H001, HY01), IC for deflection distortion correction (Q302), IC for

POP and Double Window signal processing (QY03), IC for closed caption control (QM01), IC for WAC control (QX01), IC for 3D-YCS (QZ01), IC for AUTOLIVE (QK06).

Differences from N5SS chassis are as follows;

1.On-screen function inside microcomputer is used. Sepa- rate IC is not used for on-screen.

2.The microcomputer does not have the closed caption function, but controls separate IC for closed caption.

3.The system uses two channels of I2C bus. One is only for non-volatile memory.

2. OPERATION OF CHANNEL SELECTION CIRCUIT

Toshiba made 8 bit microcomputer TLCS-870 series for TV receiver, TMP87CS38N-3320 is employed for QA01.

With this microcomputer, each IC and circuit shown below are controlled.

(1)CONTROL OF VIDEO/CHROMA/DEF SIGNAL PROCESS IC (Q501 Toshiba TA1222AN)

•Adjustments for uni-color, brightness, tint, color gain, sharpness and PIP uni-color

•Setting of adjustment memory values for sub- brightness, sub-color and sub-tint, etc.

•Setting of memory values for video parameters such as white balance (RGB cutoff, GB drive) and gcorrection, etc.

•Setting of video parameters of video modes (Stan- dard, Movie, Memory)

(2)CONTROL OF A/V SWITCH IC (QV01 Toshiba TA1218N)

•Performs source switching for main screen and sub screen

•Performs source switching for TV and three video inputs

(3)CONTROL OF NON-VOLATILE MEMORY IC (QA02 Microchip 24LC08BI/P)

•Memorizes data for video and audio signal adjust- ment values, volume and woofer adjustment val- ues, external input status, etc.

•Memorizes adjustment data for white balance (RGB cutoff, GB drive), sub-brightness, sub color, sub tint, etc.

•Memorizes deflection distortion correction value data adjusted for each unit.

(4)CONTROL OF U/V TUNER UNIT (H001 Toshiba ELA12L, HY01 Toshiba EL922L)

•A desired channel can be tuned by transferring a channel selection frequency data (divided ratio data) to the I2C bus type frequency synthesizer equipped in the tuner, and by setting a band switch data which selects the UHF or VHF band.

(5)CONTROL OF DEFLECTION DISTORTION COR- RECTION IC (Q302 Toshiba TA8859P)

•Sets adjustment memory value for vertical ampli- tude, linearity, horizontal amplitude, parabola, cor- ner, trapezoid distortion.

(6)CONTROL OF POP & Double Window SIGNAL PRO- CESS IC (QY03 Toshiba TC9092AF, QY91 Sony CXP85116B-514Q)

•Controls ON/OFF and 9 pictures serch of POP.

(7)CONTROL OF CLOSED CAPTION/EDS (QM01 Motorola XC144144P)

•Controls Closed Caption/EDS.

(8)CONTROL OF WAC (QX01 Toshiba TC9097F)

•Controls Wide Aspect.

(9)CONTROL OF 3D-YCS (QZ01 Toshiba TC9086F)

•Controls ON/OFF of 3 Dimension Y/C separator.

(10)CONTROL OF VERTICAL AMPLITUDE (QK06 Toshiba TMP87CM36N)

•Controls Wide Mode.

(11)CONTROL OF OSD (Do not I2C BUS) (QR60 Fujitsu MB90091)

•Controls of OSD Menu.

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