Replace Altera EPCS4 with M25P40

Hello folks,

We currently use epcs4 as altera FPGA's configuration device, but the price of epcs4 is quite expensive.

I found that ST's m25p40 can be used to replace the epcs4 in this link:http://fpgaforum.blogspot.com/2006/03/any-replacement-for-altera-epcs_19.html

And I found in some designs, m25p40 is used as the configuration device.

But in the datasheets of EPCS4 and m25p40, I found there is a difference about instruction "Read silicon ID" between them:

EPCS4: 1010 1011 (ABh)

M25P40: 1001 1111 (9Fh)

I'm wondering whether there is any problems if using M25P40 to replace epcs4, as the "Read silicon ID" instructions are different.

Thanks!

Br,

Tang