A second version of the RAMDAC card using the Booktree Bt450. In the first version the displayed screen was sometimes influenced by the power flow around.
In this version I used the design default layout mentioned in the datasheet of the Bt450 and yes, the result is a much more stable screen – perhaps in quality near to the Atari ST at 640×400.
The default location of the RAMDAC is the port address 0x42/0x43.
The Bt450 is able to handle up to 16 colors in mode 5 of the MIVAC chip.
In addition to the design changes mentioned above, I also made connections to the I2C information system of all modern monitors.
The I2C information of the monitor can be routed to the I2C lines on the backplane.
The last feature is only for playing and nothing has been tested here.
Published at easyeda: https://easyeda.com/marten_7544/mskzio-ramdac-bt450
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