Service manual of MT31AS
The flow of small signal
5.3.3. Control BUS
HDMI interface includes three groups of differential data, a group of differential clock
transmits media data, and a group of I2C control bus used to EDID and HDCP protocol
communication. When the communication is failure, it may be not able to play FULL HD video.
TUNER transmits the decoded IF signals by IF differential data line. Main IC feedbacks IF-AGC to
control the intension of TUNER
’
s output signals and uses I2C bus to achieve options such as
channel selection and setting. VGA port includes I2C bus. It is used to UART debug and transcribe
factory data expect EDID communication. FLASH communicates with main IC by SPI BUS. Main IC
needs to communicate with FLASH frequently in power on. IR board receives infrared signal then
Main IC identifies the decoded signals. Key board outputs analog level to Main IC and the signal is
transformed to digital code by ADC to be identified. Main IC controls the BL by BL_ON (BL on/off
enable) and DIMMING (BL intension adjust) signals.
