Xilinx OPB External Memory Controller

I have a system on a Virtex4-FX with a MicroBlaze and the xilinx opb_emc (v 2.00). I thought I set up the parameters properly to match the async FLASH memory chip that I have on my development board, but the controller does not look to be respecting the settings I set.

I have the system running at 100MHz, and the external FLASH chip is a

70ns Spansion part. On a read, the address needs to stay valid for 70ns, but it's only staying valid for ~2 cycles (where the cycles are based upon the 100MHz clock, and observed using ChipScope). The same happens for a write, for say putting the chip into CFI mode, the write line is only staying asserted for ~2 cycles when it needs to be 70ns as well.

I tried increasing the timespec values for the ipcore, but the external operation stayed exactly the same even if I doubled the requirements.

Has anyone seen or experienced similar problems?

TIA,

Mike Koss

Reply to
morphiend
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Mike, Did you set the memory type to asynchronous? What you describe looks like synchronous mode. Jan

Reply to
Jan Pech

Yes I have it currently set to asynchronous, because the part I was interfacing to is asynchronous (no clock input). Is this not the correct assumption?

Reply to
morphiend

Your assumption is correct. But from the behavior you described I got the feeling the mode had been set to synchronous. When you choose asynchronous mode of the EMC, the controller takes into account the timing parameters. If you set the synchronous mode, the only timing related parameter EMC looks at is the pipeline latency (1 or 2 clock cycles). At least OPB_EMC v. 2.00.a behaves this way. Jan

Reply to
Jan Pech

I double-checked my project and it was set to async mode for the memory bank. I tried changing it to sync (to see what happens) and it changed from two-cycle to one-cycle. That was what I expected: it still didn't work.

I'm using the latest ISE/EDK 8.2 and the opb_emc v.2.00.a. Looks like I'm going to have to file a webcase for the problem and see what Xilinx has to say.

Reply to
morphiend

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