Hitachi CL43WP910TAN, Service Manual

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be accessed from the EPROM/MTP (I002). These lines are also connected to I003 if an SRAM is to be fitted in future.
Normally these lines will be changing state (0V to approx. +5V). By placing an oscilloscope on pin 12 of the EPROM/MTP
(I002) it can be confirmed that the microcontroller is operating successfully. In this case, this line should be changing state
very frequently.
External Memory Interface Data Lines
Pins 63 to 70 are the 8 data lines needed for receiving data from the EPROM/MTP (I002). If an SRAM were to be fitted in
position I003, then these lines would be used to transfer data from the microcontroller to the SRAM. Under normal
circumstances these lines change from LOW (0V) to HIGH (approx. +5V).
Ground Connections
Pin 9 (GNDM) is the ground connection (0V) for the external memory interface. This should be free of noise to enable
successful communications between the microcontroller and the EPROM/MTP (or SRAM).
Pin 35 (GND) is the digital ground connection (0V) for normal operation of the device.
Pin 62 (GNDA) is the analogue ground connection for the DAC and phase lock loops (PLL’s).
Supply Connections
Pin 10 (VDDM) is the +5V supply for the external memory interface. Without this supply, the microcontroller cannot
communicate with the EPROM/MTP (or SRAM).
Pin 34 (VDD) is the main digital supply voltage to the IC (5V 10% tolerance).
Pin 52 (VDDA) is the analogue supply voltage for the DAC’s and PLL’s (+5V). These connections are all joined together to
the +5V standby rail of the television, ensuring that the microcontroller operates even in the standby state.
Crystal Oscillator Connections
Pin 11 is the 4MHz crystal oscillator input (OSCIN).
Pin 12 is the 4MHz crystal oscillator output (OSCOUT). By connecting a x100 scope probe to pin 11, it can be seen if a
4MHz sine wave is present at the oscillator input to the microcontroller.
Reset Connection
Pin 54 is the active low RESET input of the microcontroller. This input is normally high (approx. +5V) under operating
conditions, but changes state when the s5V power supply is typically below +4.5V. In this circumstance, the reset
IC (I011) pulls pin 54 low until the input of it is above +4.5V. The diode (D005) ensures that the capacitor (C024)
discharges quickly when the standby supply falls, so that the reset operates quickly. The capacitor (C024) charges up
slowly when the s5V supply is restored, ensuring that there is some hysteresis.
Infra-red (IR) Receiver Input
Pin 25 is the IR receiver’s filtered output. This input from the IR receiver consists of PWM pulses between 0V and +5V
which are decoded by the microcontroller into useful commands from the handset. When a valid command has been
decoded, the Red LED on the front of the TV will briefly flash.