I'm using Silicon Motion's SM750 GPU and ADV7343 encoder for both VGA and CVBS outputs. SM750 provides 2 VGAs and 24bit flat panel outputs and I'm using 1 VGA and 24bit RGB flat panel output for CVBS.
I applied 27MHz signal to ADV7343's Clk_a pin and wrote to registers this values:
And colored Sd test patterns worked with PAL outputs. After that I connected SM750's pixel clock output with ADV7343's clk_a pins directly (via 0R resistor). I programmed registers with these table values (Table 81).
I checked the resolution in Windows OS and set resolution 640x480, 60Hz. But there is no video output. I checked frequency of pixel clocks and saw 25.175 MHz. I searched the engineer zone's page and understood there is allways 27 Mhz clock must applied clk_a pin. If I use 800x600, 60Hz resolution, pixel clock will arise 40 Mhz. I'm confused.
I believe my circuit is true but there is an another problem and I can't see. What should i do or which frequency applied to clk_a pin? Is 27 Mhz clock freq. necessary?
Thanks for all your reply.