Atmel ATmega Video generator with SDRAM

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This projects uses 8MByte SDRAM from a 168 pin DIMM SDRAM and generates videosignal for a VGA monitor with a resolution of 512x480 pixels with 256 colors at 60Hz using mega8515.

The project uses burst mode of SDRAM, which can feed up to 512 bytes without MCU help. This means that MCU can do anything (i.e. generate another graphics) during that time. 8MB SDRAM can be used to store up to 32 frames, so you can display one frames while generating another one.

So far this project works but is not yet complete.

The text demo application shows a text stored in flash memory. Graphics demo receives a BMP image large 512x512 pixels with 256 colors.

The data throughput of SDRAM is as fast as the AVR clock, and the CPU load is much lower than if DRAM or SRAM is used.

Images

Here is a test image in the graphics mode. This picture shows the construction of the circuit: Besides the mega8515, SDRAM, the RAM DAC, a 18432MHz clock and a delay line (or just several gates in series) requires no additional components.
Text mode (rendered in graphics).

Atmel ATmega Video generator with SDRAM

Images

Files