In SX Microcontrollers, SX/B Compiler and SX-Key Tool, peterverkaik wrote:

I adapted the sxvideo revD pal version to use port B pins (attached) on a sx18.
It runs currently @50MHz.

[b]Is it possible to run this @20MHz and what needs to be changed to make that work?
[/b]
I have a remark regarding the resistor values used.

Current setup
VsyncPin --[1000]---+
                    +----  //  ------+
VoutPin  --[470]----+    cable       |
                                    [75]
                                     |
                                     V

The output impedance equals 1000//470 = 320 ohm. So there is an impedance mismatch.

Alternative setup
VsyncPin --[625]----+
                    +----  //  ------+
VoutPin  --[268]----+    cable       |
                    |               [75]
                  [125]              |
                    |                V
                    V
The output impedance equals 625//268//125 = 75 ohm.
I expect this to give a sharper picture (no reflections) when a long videocable (approx. 10 meters) is used
compared to the current setup. [b]Any comment on this?[/b] I have not tried this out yet as I don't have
a long video cable.

regards peter

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