Honored Contributor
Honored ContributorHi zurkov,
nCONFIG is an FPGA input pin, and you tie it to VCC33, so it should actually be high. The FPGA cannot pull it low, only your reset button. Is maybe your reset button stuck, or did you accidentally solder in a normally-closed button? Also, I don't see your MSEL pins. I can only guess that they are maybe pins 2, 4 and 10 on your "CONF1" header; see table 8-3 of the Cyclone IV Device Handbook to find out how you must connect them. You use 3.3V for the JTAG header. I don't know how to interpret the Device Handbook here; it says JTAG works between 2.5 and 3.3V (section "Configuration and JTAG Pin I/O Requirements", section 8), but figure 8-23 explicitly says you must use VCCA, which is 2.5V. I'm not sure if this could be a problem. Also, figure 8-23 in the Device Handbook shows a 25 Ohm resistor close to the configuration memory; again, not sure if this could cause truble; I gues snot. I recently designed a board with a EP4CE40, and had similar issues with the prototype. Eventhough JTAG is supposed to work independently of any configuration scheme, it won't be detected in the JTAG chain if there's something wrong with the configuration scheme. So it might be that the JTAG issues go away once you fixed the connection to the configuration memory. Best regards, GooGooCluster
