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SingMai Electronics
The back porch value is also used to subtract an offset from the output luma value (remove
the syncs).
aCVi_Procamp.v
The low pass filtered luma is conditioned by the processing amplifier. First the black level
offset is subtracted from the luma signal to set the black level at zero. The luma is then
amplified to provide a 960 code (10 bit) output for a 100% colour bar input. The luma output is
valid on the rising edge of the 74MHz clock.
The low pass filtered chroma outputs are amplified separately to provide a nominal 700mV
output for a 100% colour bar input. These outputs are then multiplexed into a Cb/Cr output.
The output is valid on the rising edge of the 74MHz clock and the Cmux output (37MHz) is
used to de-multiplex the video (Cmux=0 = Cb, Cmux=1 = Cr).
The SPG also provides Vout (vertical), Fout (frame ID for interlaced video) and Hout
(horizontal) synchronizing pulses.
aCVi_data.v
The aCVi interface allows for the bi-directional transmission of control data between the
transmitter and receiver. The data is transferred during to two dedicated lines of the vertical
blanking interval, one for transmitter to receiver transmission, the other for receiver to
transmitter.
One byte of data is sent for each line, allowing a maximum of 60 bytes to be transferred each
second, (for a 60Hz frame rate).
The format of the data transfer is shown in Figure 17.
Figure 8 aCVi Data format.
The format is the same regardless of the direction of transfer.
PT22 User Manual Revision 0.5
Page 17 of 28