will.stevensI'm sure I'm not the only person to have a component drawer full of old DRAM chips, kept in the hope that a use can be found for them one day.
The 4164 is almost ideally suited for this project. It has separate data in and out pins - the PIC writes data through the data in pin, and the data out pin provides the data for the video signal. Each line of 256 pixels corresponds to a row in the DRAM. The /CAS signal is provided by the PWM output of the PIC.
The DRAM refresh timing requirements are not met, but this does not appear to cause any problems. I guess that the datasheet-specified refresh timing are conservative.
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I worked on the bringup of a DSP PCI card at one point. The firmware engineer had forgotten to enable refresh of the DRAM, but it worked fine for weeks for me because my code constantly hammered the memory. Maybe my office was at just the right temperature or something, but we never saw failures until other people started using the card. Sometimes you can get away with stuff :-)
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