using extra space in serial rom

Hi,

I notice that there is a way to store additional data in "general purpose memory" section of EPCS device, from the FPGA, with ALT_ASMI megafunction.

I looked at http://www.altera.com/literature/ug/ug_altasmi_parallel.pdf but on which address does "general purpose memory" section begin (or on which address does "configuration" section end) ?

Does FPGA need to read at a particular address to find out the end address of "configuration" section in EPCS ?

Have anyone made such thing ?

My goal is to store for example min and max values of an analog input and to extract them by examining the EPCS.

All ideas are welcome, thanks.