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Re: SDRAM in line resistors
The resistors are there to cancel out ringings on the lines. They
should be placed near the end that drives the line for best effect.
Address and control lines are driven by ETRAX 100LX, thus the resistors
for these signals should be close to ETRAX 100LX.
The data bus is driven by both ETRAX 100LX and the SDRAM, but there
shouldn't be double resistors because that could slow down the signals
too much. I think a placement close to the SDRAM is best for the resistors
on the data signals, since read is more timing critical than write. The
SDRAM outputs are usually also more noisy than the ETRAX 100LX outputs.
On Mon, 2 Dec 2002, Steve Jones wrote:
> When fitting SDRAM to the Etrax 100LX is it recommended to fit 22R
> resistors in line to the address, data and the control signals. If so
> for data bus should they be next to the Etrax chip or SDRAM chips, or
> have two lots fitted.
> Steve Jones