这里主要是针对EP3C系列FPGA的Nios程序固化到EPCS中的方法做简要说明。
硬件SOPC
1、要固化程序到EPCS，在SOPC Builder中首先需要添加EPCS_Controller核，此外，CPU的reset vector设置为EPCS_Co
ntroller,Exception Vector一般设置为SDRAM即可。
2、生成该nios_cpu。对于EP3C系列的FPGA来说，在生成cpu后，会出现与EPCS_Controller相关的4根引线（如图），
这在之前的EP2C等早期系列的FPGA中是没有的，因为系统已经默认完成了相应的设置，而EP3C是需要自己来对这些引脚设置的，
这一点尤为要注意，下面就来具体说明一下。
这4根信号线分别为（EP3C10F256）：
EPCS_DATA0 -> H2
ASDO -> C1
nCS0,(Flash_nCE) -> D2
DCLK -> H1
在对这4根引线进行引脚分配的时候，要在Device中将这些双功能引脚功能都设置为regular I/O Pin，
否则会出现错误：
比如:Error：Can't place multiple pins assigned to pin location PIN_H2
......
对这些引脚做完这些设置后，即可进行编译、下载了(引脚分配如下图)。
另外，在使用Quartus II 10.0高版本编译Cyclone IV器件的时候，可能在Device->Dual Purpose里面的DCLK等引脚没有
USE AS Regular I/O选项，用户就无法给DCLK这些引脚指定Pin Assignment。
这时的解决办法是：
打开工程的.qsf文件，加上以下几句(若存在对这4个引脚的其它类似配置信息时，先删除)：
set_global_assignment -name RESERVED_FLASH_NCE_AFTER_CONFIGURATION "USE AS REGULAR IO"
set_global_assignment -name RESERVED_DATA0_AFTER_CONFIGURATION "USE AS REGULAR IO"
set_global_assignment -name RESERVED_DATA1_AFTER_CONFIGURATION "USE AS REGULAR IO"
set_global_assignment -name RESERVED_DCLK_AFTER_CONFIGURATION "USE AS REGULAR IO"
保存并编译，就可以正确读写EPCS了。
软件Nios
1、在nios中建立相应工程，并编译。
2、编译完成之后，打开FLASH Programmer。
勾上Program FPGA configuration data into hardware-image region of flash memory（将FPGA的配置文件写入Flash(EPCS)），
并设置对应的.sof文件Hardware Image设置为Custom，Memory设置为EPCS_Controller，offset为0x0，
不勾选Program a file into flash memory（可将二进制文件写入Flash）。
完成后如图所示：
以上所有设置完成后，Apply，然后Program Flash即可。烧写成功后，会有如下信息：
#!/bin/sh
#
# This file was automatically generated by the Nios II IDE Flash Programmer.
#
# It will be overwritten when the flash programmer options change.
#
cd D:/MySoftwares/QuartusII/Mywork/sopc_project/led_test/software/led_test/Debug
# Creating .flash file for the FPGA configuration
"$SOPC_KIT_NIOS2/bin/sof2flash" --epcs --input="D:/MySoftwares/QuartusII/Mywork/
sopc_project/led_test/led_test.sof" --output="led_test.flash"
Info: *******************************************************************
Info: Running Quartus II Convert_programming_file
Info: Command: quartus_cpf --no_banner --convert --device=EPCS128 --option=led_t
est.opt D:/MySoftwares/QuartusII/Mywork/sopc_project/led_test/led_test.sof led_t
est.pof
Info: Quartus II Convert_programming_file was successful. 0 errors, 0 warnings
Info: Peak virtual memory: 70 megabytes
Info: Processing ended: Wed Mar 30 12:34:48 2011
Info: Elapsed time: 00:00:02
Info: Total CPU time (on all processors): 00:00:02
Info: *******************************************************************
Info: Running Quartus II Convert_programming_file
Info: Command: quartus_cpf --no_banner --convert led_test.pof led_test.rpd
Info: Quartus II Convert_programming_file was successful. 0 errors, 0 warnings
Info: Peak virtual memory: 68 megabytes
Info: Processing ended: Wed Mar 30 12:34:51 2011
Info: Elapsed time: 00:00:03
Info: Total CPU time (on all processors): 00:00:02
# Programming flash with the FPGA configuration
"$SOPC_KIT_NIOS2/bin/nios2-flash-programmer" --epcs --base=0x01001800 --sidp=0x0
1002018 --id=1794073991 --timestamp=1301451768 --instance=0 "led_test.flash"
Using cable "USB-Blaster [USB-0]", device 1, instance 0x00
Resetting and pausing target processor: OK
Reading System ID at address 0x01002018: verified
: Checksumming existing contents
00000000 : Verifying existing contents
00010000 : Verifying existing contents
00020000 : Verifying existing contents
00000000 : Reading existing contents
00010000 : Reading existing contents
00020000 : Reading existing contents
Checksummed/read 54kB in 1.4s
00000000 ( 0%): Erasing
00010000 (33%): Erasing
00020000 (66%): Erasing
Erased 192kB in 1.9s (101.0kB/s)
00000000 ( 0%): Programming
00010000 (33%): Programming
00020000 (66%): Programming
Programmed 139KB +53KB in 3.3s (58.1KB/s)
Did not attempt to verify device contents
Leaving target processor paused
# Creating .flash file for the project
"$SOPC_KIT_NIOS2/bin/elf2flash" --epcs --after="led_test.flash" --input="led_tes
t.elf" --output="epcs_controller.flash"
# Programming flash with the project
"$SOPC_KIT_NIOS2/bin/nios2-flash-programmer" --epcs --base=0x01001800 --sidp=0x0
1002018 --id=1794073991 --timestamp=1301451768 --instance=0 "epcs_controller.fla
sh"
Using cable "USB-Blaster [USB-0]", device 1, instance 0x00
Resetting and pausing target processor: OK
Reading System ID at address 0x01002018: verified
: Checksumming existing contents
00020000 : Verifying existing contents
00020000 : Reading existing contents
Checksummed/read 42kB in 1.1s
00020000 ( 0%): Erasing
Erased 64kB in 0.6s (106.6kB/s)
00020000 ( 0%): Programming
Programmed 23KB +41KB in 0.7s (91.4KB/s)
Did not attempt to verify device contents
Leaving target processor paused
烧写完成，Reset或者断电重启，烧写在EPCS中的程序即开始运行了。
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