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Re: dma 8 bit peripheral
On Mon, 25 Nov 2002, Steve Jones wrote:
> I am putting a 8 bit wide NAND flash (Samsung) onto the ETRAX MMC chip.
> These have a data bus but no address bus as such (address is written via
> data bus). I would like to use DMA as these devices have a page mode
> where the internal address auto increments (512 Bytes circular) to
> transfer data to and from it in 512 byte blocks from 16 Bit SDRAM.
> Could I connect as follows
> CE# CSR0,
> WE# WE0|CSR0
> RE# RD|CSR0
> ALE Gen IO
> CLE Gen IO
> D0-D7 D0-D7
> Set access to speed to 50nS etc.
> ETRAX DREQ to ETRAX General IO pin
> To use DMA use Burst Mode. Set DMA Counter to 512 bytes. Assert IO pin,
> DMA should continue until counter hits zero where DMA should stop.
> Unassert IO pin to unassert DREQ. Would this work, or could I set DREQ
> to permanently asserted and use DMA counter to start and stop it etc.
It should be possible to set DREQ permanently, and control the external
DMA with only the counter and start/stop bit.
The connection you have proposed will not work, since the CE# to the NAND
flash needs to be low throughout the operation. If you control the CE#
from a general IO instead, I think it will work.