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GENERAL OUTPUT CONNECTIONS
74HC595 SHIFT REGISTER OUTPUTS
STORAGE-REGISTER CLOCK OUTPUT (RCLK)
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Pin 20 of the microcontroller is connected to the rising edge (positive triggered) input (pin 12) of I006. This line is normally
low when not communicating with the device or when shifting data into it. Once the full 8-bits have been shifted in, the
RCLK line rises in order to latch the data to the device's outputs.
SHIFT-REGISTER CLOCK OUTPUT (SCLK)
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Pin 17 of the microcontroller (MMU4) is used to transfer the data into to the 8-stage shift-register on the rising edge of the
SCLK. 8 clock pulses are needed to transfer 8 bits of data into the shift register.
SHIFT-REGISTER DATA OUTPUT (SI)
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Pin 21 of the microcontroller is used as the data line input to pin 14 of the shift register. When this line is HIGH, and the
SCLK changes from low to high, the first bit of data (logical 1) is shifted into the register. When this input is low, the first bit
of data is '0', on the rising edge of the SCLK.
EEPROM WRITE ENABLE OUTPUT
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Pin 22 is the E2 write enable output line, which is connected to pin 7 of the EEPROM (E2). When this output is HIGH
(approx. +5V), the E2 cannot be written to (write disable) but data from the device can be read. When this output is low
(0V), then data can be written to the E2. This hardware line helps to protect the E2 from inadvertent write operations,
which could occur under abnormal circumstances.
ON/OFF OUTPUT
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Pin 28 is the On/Off line which turns On (LOW) /Off (HIGH) the secondary supplies (+B, +16V audio rail, +8V and +5V).
The standby +5V and+10V rails are unaffected when this output is HIGH (TV in the standby state). Under normal
operating conditions, this output will be low when the TV is NOT in the standby condition.
ON/OFF 2 OUTPUT
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Pin 29 is the On/Off 2 line which turns On (LOW) / Off (HIGH) the DTT/ASW sub-power supply.
DTT RESET OUTPUT
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Pin 31 is the DTT reset line which is asserted HIGH (+5V) on power-up and shutdown of the DTT module. Under normal
operating conditions when the TV is powered up, this line is low.
I2C DISABLE OUTPUT
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Pin 33 is the I2C disable output which prevents the main chassis I2C bus from being connected to the I2C bus of the
microcontroller (I001) and E2 (I002). This line is normally HIGH when the TV is in the standby state. This output is
inverted using the 74HC04 hex inverter IC (I004) and in connected to pins 5 and 6 of I007. In the standby condition, pins 5
and 6 of I007 (74HC4066) are low and the M.SDA and M.SCL (microcontroller) lines are disconnected from the SDA and
SCL (main chassis) I2C lines. When writing to the E2, the I2C disable output is also pulled high, to ensure that successful
writing of the data has occurred (e.g. to log fault diagnostics when the TV fails to power-up and the main chassis I2C bus
is low).
SCART DISABLE OUTPUT
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Pin 39 is used to disable the RS232 transmit and receive lines from pins 10 (Rx) and 12(Tx) of scart socket 2. This is
necessary when the TV is functioning normally. However, when the TV is in service or diagnose modes, then this output
will be low to enable connection of the RS232 lines of the microcontroller to the scart socket.
MUTE OUTPUT
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Pin 40 is the mute output for the on-board audio amplifiers. This output is HIGH when the amplifiers are in the mute
condition (e.g. Standby). If the user has chosen to use the internal speakers, then under normal operating conditions, this
output will be LOW. When powering down, this output will quickly rise to mute the speakers, to prevent any unwanted
'popping' noises from being heard.
GREEN LED OUTPUT
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Pin 41 is the green LED output, which is only used on the D8 chassis fitted with a DTT module. This output is high when
the green led is ON. When the DTT module is in the partial standby state or when recording a digital terrestrial
programme, then this LED will be ON and will be mixed with the red LED to produce an amber colour. When the DTT
module is connected via the telephone line and receives mail, then this LED will flash periodically to indicate this
condition.
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When the TV first has power applied to it, then the green LED will be ON. Soon after, though, this LED should extinguish
to indicate that the TV is operating correctly. NOTE: This is one of the easiest ways to check that the microcontroller is
running the programme code correctly in the EPROM/MTP. If the green led remains ON, then the microcontroller or
EPROM/MTP has a fault preventing the code from being executed correctly.
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