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Old 5th Apr 2011, 2:01 pm   #62
pitbuell94
Retired Dormant Member
 
Join Date: May 2009
Location: Fresnes, France
Posts: 124
Default Re: 819 line standards convertor.

Hi,

Small information concerning my previous post.

The main clock frequency is 50 MHz.

About unit 625:

This unit allows normal function concerning the TDA8708A in mode 2.

It supply signals SEL TDA8708, WR_CLK, GATE A and GATE B to the TDA8708A.

GATE A and GATE B are complement of signal Hsync and Burst Blanking coming from LM1881.
These signals allows the TDA8708 to run in mode 2 => see data-sheet.

WR_CLK are sample frequency for actually in my design 512 dots per line.

SEL TDA8708 is signal to select the right video input when necessary.

It supply also signals START_819_INT, RST_ FIFO_INT, VIDON_625_INT, WR_CLK_INT

START_819_INT allows to start the read process.
RST_FIFO_INT : reset the FIFO pointer at each field.
VIDON_625_INT : allow the write operation concerning FIFOs.
WR_CLK_INT: this is the write clock for 512 pixel per line.


About unit 819.

FIFO1_RD_EN and FIFO2_RD_EN, RD_CLK_INT, VIDON_819, SYNC_int, RD_CLK_EXT, START_819_INT.


FIFO1_RD_EN and FIFO2_RD_EN are signals driving the FIFO 1 and 2.
By correct driving, you have 4 lines in place of 3.

RD_CLK_INT: this is the frequency reading signal for 819 operation.

VIDON_819 : this one allows the interpolator to supply the correct data depending to available video signal or not.

SYNC_INT: this is the complete synchro for horizontal and vertical information.

RD_CLK_EXT:this is the frequency reading signal for 819 operation concerning TDA8702 operations

START_819_INT:this signal comes from 625 unit. it drive the 819 unit to start the read process.

UNIT FIFO 1 and 2:

This unit is drived by unit 625 and 819.
it supply a video signal without any synchro signal.

Output of this unit go true to the interpolator.

unit INTERPOLATOR:

By mixing the signal coming from unit 819 and FIFOs, the interpolator add to the video signal coming from the FIFOs the SYNCHRO signal.

When VIDON is off and SYNC_INT is off, the signal VIDEO819 => black level or 0100 0000.

When VIDON is ON, signal VIDEO819 is the value of FIFO1 (and/or) FIFO2.

When SYNC_INT is ON, the value of VIDEO_819 is sync level or 0000 0000.

Have a good day.

Frédéric Cabanes.
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