how can we access sdram from atmel 8051

As SDRAM is dynamic, and the bogstandard 8051 doesn't support dynamic RAM (I don't know if any variants do), you need extra hardware. Several controller designs are available on the web, like this:

but I don't know of any ready-made ones you can buy (because I haven't looked), so you'll also need a PLD of some sort to put it in. If it's an ordinary 8051 running at 5V, finding a suitable 5V PLD is a bit of a pig these days.

Paul Burke

Finding 5V SDRAM is probably even harder :) There were old designs around that did DRAM in SW, so with faster

80C51 variants, and faster SDRAM that could also be an option. Usually the bandwidths are low, bordering on the slowest the device can tolerate. For faster bandwidths, the CPLD will be needed.

- something like an Atmel ATF1502BE/1504BE, or a Xilinx Coolrunner

-jg