Panasonic BT-M1950Y Service Manual page 101

3. ICs connected to the 12C bus
3-1 EEPROM
The ST24C02A (ST24BM-1400) non-volatile 256 byte electrically erasable programmable read only memory is used
in order to hold the status at the lime of the previous system startup. The ROM can be accessed externally via a Z
connector provided with pins for EXT SCL, EXT SDA and GND. The I2C bus can be controlled from the
Z
connector by the remote control code FBH (in practice, the monitor code 1 FH header is needed). (The signal from the
MPU is stopped at this time.) Release is by F9H (in practice, the monitor code 1FH header is needed). Although data
are contained in the ROM when supplied as a service part, in production, the data are entered from the Z connector.
3-2 Video processor (TDA4672) and picture signal improvement (TDA4680)
Video signal control lCs used for the signal PB ASS'Y. IC control is from the MPU via the bus connecting the MPU
and signal PB ASS'Ys. Refer to the signal PB ASS'Y description.
3-3 TV V DEF processor (CXD-201 BQ)
Deflection control IC used on the deflection PB ASS'Y. Connect via the signal PB ASS'Y. Data from the MPU are
transmitted by a bus. Refer to the deflection PB ASS'Y description.
4. Front panel
User interfaces controlled by the MPU are located on the front panel. The five control knobs are Volume, Phase,
Chroma, Bright and Contrast. Adjustments are converted from analog to digital form and controlled by the MPU. The 17
buttons are Input Select
(4),
Underscan, Pulse Cross, Color Off, Blue Check, Memory Mode, Ext Sync, Menu Control
(6) and Degauss. The set status is indicated by LEDs.
5. Infrared detector element (remote control receiver)
The pulse signal from the infrared detector element goes to the MPU PWC port. The pulse width is measured and data
are read from the
O
and 1 serial bit train.
Poor shield case grounding can impede element performance. Also, a pullup resistance of about 10 Kohms needs to be
inserted between the 3 pin terminal (-OUT) and the MPU port. Signals are not detected if the resistance is absent.
6. Audio volume circuit
The audio volume circuit converts the PWM pulse from the MPU into a O - 12 V DC level pulse. Duty is O % at volume
0 and 99.6 % at maximum. Resolution is 500 ns, period is 1.28 us and frequency is 7.81 kHz.
7. Sync detector circuit
A Low output is produced when a Y sync input is present and a High output when absent. The output goes as the -sync
detector signal to the MPU pin 30 and No Sync is detected from the signal. The signal also goes to the SA connector
pin 9. In absence of sync, No Sync is displayed on the screen.
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