cyclone IV device handbook.pdf有比较详细的说明。

conf_done当device被配置文件后，为高电平

nconfig 程序正常运行为高电平

FPGA里面有一个internal oscillator for initialization，cyclone IV E里面是40M

CLKUSR

during POR(power up reset),the device resets,hold nstatus and conf_done low.

while nconfig  low,the device is in reset.you can begin reconfiguration by pulling nconfig pin low

when nconfig goes high,the device exits reset and release the open-drain nstatus pin,which is then pulled high by an external 10k pull-up resister

after nstatus is released,the device is ready to receive configuration data and the configuration stage starts.

cofiguration data is latched into cyclone iv device at each DCLK cycle

DATA0，DCLK , nCSO , ASDO连接EPCSX

the nCSO pin function as FLASH_nCE pin in AP mode,the ASDO pin functions as the DATA[1] pin in AP and FPP modes.

the nCEO is left unconnected or used as a user I/O pin when it does not feed nCE pin of another device.

JTAG下载口TDI , TDO , TMS , TCK

当使用JTAG，确保nCE是低电平