Re: 4MB flash interface to DM641?

Not too hard...

If you've got a couple of GPIO pins free, connect them to A20/21 on the flash with pulldown resistors. To switch banks, enable the appropriate GPIO as outputs and toggle them as necessary.

If you don't have GPIO available but have an /ACEx pin free, you could use it to write to a 74*273 octal flip flop, using a 74*00 as glue. Connect /MR on the part to /RESET on the DSP so you come up in the first bank. Write the desired bank # to the approriate /ACEx memory space to choose the active bank.

GM


vishnus wrote:
Hello folks,

I am designing a custom TI DM641 DSP board for an image processing
application. I want to design a 4MB flash interface to the DM641 DSP to
store program code and other data.

However, I am faced with the following problem: the DM641 has only 20
address lines, which means that it can natively access only 1MB of flash
memory.

What would be the easiest (and maybe cheapest) way that will allow me to
access 4MB of flash memory using only 20 address lines?

A similar board - the Spectrum Digital DM642 evaluation module -
implements paging using an FPGA.

However, I do not want to use an FPGA since it would drive up the cost of
the product.

Your advice will be greatly appreciated.

Thanks,

--Vishnu


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