Hitachi 17LD4220 Service Manual page 24

DATA OUTPUTS
RED
GREEN
BLUE
DATA CLOCK OUTPUTS
DATACK
INPUTS
RAIN
GAIN
BAIN
HSYNC
VSYNC
SOGIN
CLAMP
COAST
17" TFT TV Service Manual
Data Output, RED Channel
Data Output, GREEN Channel
Data Output, BLUE Channel
The main data outputs. Bit 7 is the MSB. The delay from pixel sampling time to
output is fixed. When the sampling
time is changed by adjusting the PHASE register, the output timing is shifted as
well. The DATACK and HSOUT
outputs are also moved, so the timing relationship among the signals is
maintained.
Data Output Clock
This is the main clock output signal used to strobe the output data and
HSOUT into external logic. It is produced by the internal clock generator
and is synchronous with the internal pixel sampling clock. When the
sampling time is changed by adjusting the PHASE register, the output
timing is shifted as well. The Data, DATACK, and HSOUT outputs are all
moved, so the timing relationship among the signals is maintained.
Analog Input for RED Channel
Analog Input for GREEN Channel
Analog Input for BLUE Channel
High impedance inputs that accept the RED, GREEN, and BLUE channel graphics
signals, respectively. (The three channels are identical, and can be used for any
colors, but colors are assigned for convenient reference.) They accommodate input
signals ranging from 0.5 V to 1.0 V full scale. Signals should be ac-coupled to
these pins to support clamp operation.
Horizontal Sync Input
This input receives a logic signal that establishes the horizontal timing reference
and provides the frequency reference
for pixel clock generation. The logic sense of this pin is controlled by serial register
0Eh Bit 6 (Hsync Polarity). Only the leading edge of Hsync is active; the trailing
edge is ignored. When Hsync Polarity = 0, the falling edge of Hsync is used.
When Hsync Polarity = 1, the rising edge is active. The input includes a Schmitt
trigger for noise immunity, with a nominal input threshold of 1.5 V.
Vertical Sync Input
This is the input for vertical sync.
Sync-on-Green Input
This input is provided to assist with processing signals with embedded sync,
typically on the GREEN channel. The pin is connected to a high speed comparator
with an internally generated threshold. The threshold level can be programmed in
10 mV steps to any voltage between 10 mV and 330 mV above the negative peak
of the input signal. The default voltage threshold is 150 mV. When connected to an
ac-coupled graphics signal with embedded sync, it will produce a noninverting
digital output on SOGOUT. (This is usually a composite sync signal, containing
both vertical and horizontal sync information that must be separated before
passing the horizontal sync signal to Hsync.) When not used, this input should be
left unconnected. For more details on this function and how it should be
configured, refer to the Sync-on-Green section.
External Clamp Input
This logic input may be used to define the time during which the input signal is
clamped to ground. It should be exercised when the reference dc level is known to
be present on the analog input channels, typically during the back porch of the
graphics signal. The CLAMP pin is enabled by setting control bit Clamp Function to
1, (register 0FH, Bit 7, default is 0).
When disabled, this pin is ignored and the clamp timing is determined internally by
counting a delay and duration from the trailing edge of the Hsync input. The logic
sense of this pin is controlled by Clamp Polarity register 0FH, Bit 6. When not
used, this pin must be grounded and Clamp Function programmed to 0.
Clock Generator Coast Input (Optional)
This input may be used to cause the pixel clock generator to stop synchronizing
with Hsync and continue producing a clock at its current frequency and phase. This
is useful when processing signals from sources that fail to produce horizontal sync
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21/09/2004