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Altera_Forum's avatar
Altera_Forum
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14 years ago

access to every address of SDRAM

I have a problem with reading and writing data on SDRAM, I need to access every address of SDRAM, this is my C code written for Nios: # include <stdio.h> # include <io.h> # define BASE_SDR...
Altera_Forum's avatar
Altera_Forum
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14 years ago

I add my two cents:

IORD/IOWR assume addresses to be offset by the width of the bus.

Then for a 32bit wide bus your logical offset 6000 would mean physical address (byte address) offset 6000*4.

You could use IORD_8DIRECT/IOWR_8DIRECT, which work with raw byte address.

However you must remind a couple of important points:

- if the device is 32bit wide, IORD will present you 8bit data, but a full 32bit access is performed. It simply discards not required bits.

- in Quartus V9 even if you had a 8 or 16 bit slave, the Avalon bus would still read a full 32bit word! Then for a 8bit slave, 4 byte reads were performed, no matter if you specify a single byte read!!! This is a sort of bug which was discussed in a few threads some time ago and AFAIK has not been fixed in recent updates.