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Using Address Line for Chip-Select?

Question asked by rkn on Jan 20, 2014
Latest reply on Feb 10, 2014 by rkn

Hi,

 

I have a simple question:

Let's assume I'm not using all the address lines for driving a SDRAM or SRAM can I use then the free address lines as chip-selects? Of course I know that I have to modify the word address in the SDRAM then to get the right lines high and low for the chip select. The question is, does the DMA controller touch these lines after supplying an address and starting to transfer data words or are the lines still valid with the latest address during the data line access? E.g. when I set A20 to high (by setting the bit in the address high) is A20 all the time high when I read 256 words via dma from external memory?

 

R.

 

P.S. I know there are the MS-lines. For some reasons I need more chip-selects then four….

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