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Altera_Forum
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18 years ago

Cyclone III AS configuration bizarreness

I am using a cyclone III (EP3C25F324C8N) with an EPCS16 configuration device. I am programming the configuration device through the FPGA with the serial flash loader. The problem is that the Cyc...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
18 years ago

I am also seeing a problem like this.

I'm using an EPCS64SI16N to configure a CycloneIII EP3C25F324C8NES (first device) and ArriaGX EP1AGX50DF780C6N (second device). The FPGAs are constantly reconfiguring. The CONF_DONE line goes high for about 350ns, then the nSTATUS transitions from high to low and the EPCS_nCS line transitions from low to high. 310ns after that the CONFIG_DONE line goes low again. Roughly 375ns after that the nCEO of the CycloneIII goes high. The nCONFIG line stays high throughout the process.

A small amount of capacitance (my scope probe is 8pF, same effect with a 20pF cap) added to the CONF_DONE line will cause a successful configuration.

The DCLK signal probed at the config device and ArriaGX looks good. 10K pullup resistors are on the nSTATUS, nCONFIG, and CONF_DONE lines. I'm not sure about adding a cap to the CONF_DONE line and then calling the problem fixed. Does anyone have any more ideas on this problem? Thanks.