Hitachi CL43WP910TAN, Service Manual

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Supply/Ground Connections
Pins 14 and 7 are the +5V and 0V supply connections respectively. This device always has +5V supplied to it, even when
the TV is in the standby state. Capacitor C042 is connected across the supply terminal for de-coupling.
Chip Enable Connection
Pin 1 is connected to the MMU3 output from the microcontroller and is used to select either the MTP or the SRAM. This
signal is inverted and output from pin 2 that is then connected to the active low chip enable input (pin 22) of the SRAM. In
this way, only one chip enable line from the microcontroller needs to be used to enable the SRAM.
I
2
C Disable Connection
Pin 5 is the I
2
C disable input from pin 33 of the microcontroller. This signal is inverted and output at pin 6 to pins 5 & 6 of
the analogue switch (I007). When the microcontroller is in the reset condition, or when the TV is in the standby state, the
I
2
C disable line is HIGH. This signal must be inverted to disable the microcontroller’s I
2
C bus from the I
2
C bus of the rest
of the chassis.
Scart Disable Connection
Pin 13 is the RS232 Scart Disable input from pin 39 of the microcontroller. This input is inverted and output at pin 12,
which is then connected to pins 12 & 13 of the analogue switch (I007). When the microcontroller is in the reset state, or
when the TV is NOT in service/diagnose modes, the RS232 transmit/receive lines MUST be disconnected from pins 10
and 12 of scart socket 2. This line must then be inverted to prevent any connection being made.
EEPROM (I005)
The M24C32 EEPROM, or E2 as it is commonly known, is a 32Kbit (4Kbyte) device that holds non-volatile data when
power is removed from the TV. This device can hold information for 100 programmes, such as the name, frequency,
standard, AV setting, speaker language setting and teletext favorite pages. The EEPROM also holds diagnostic fault codes
used to help identify previous faults with the chassis (see separate section that deals explicitly with this). The E2 also holds
factory aligned parameters, such as the geometry, white balance, tuner AFC/AGC, model type, cathode level, etc. The E2
also holds the user’s preferential settings, such as the volume, balance, contrast, brightness, etc. Data is written to/ read
from the device using the standard Philips I
2
C protocols.
Supply/Ground Connections
Pins 8 and 4 are the +5V supply and ground (0V) connections respectively. The EEPROM is powered from the +5V
standby rail so that it always has power to it, even when the TV is in standby.
I
2
C Connections
Pin 5 is the I
2
C Data line needed to transfer serial data between the microcontroller and itself. Data is changed when the
clock line is low and latched on the rising edge of the I
2
C clock.
Pin 6 is the I
2
C clock line needed to synchronise the I
2
C data transfer. 9 clock pulses are needed for the 8-bit data and an
acknowledge bit. The I
2
C master clock originates from the microcontroller and operates at a frequency around 100KHz.