The process of downloading configuration data for an fpga device is often referred to as a programming procedure. There are three commonly used download file formats, which also correspond to three download modes.
1. .sof file (static ram of file), the file is directly downloaded to the static ram inside the fpga device through the jtag interface. The essence is to determine the generated circuit structure by configuring the static ram. This programming method will cause the program to be lost because the static ram is powered off and not saved after the fpga device is powered off, that is, the program is powered off and not saved.
2. .jic file (jtag indirect configure file), which is indirectly written to the epcs power-down storable device through the jtag interface. The so-called indirect means that the fpga device passes through the fpga device in the process of programming, and the fpga device writes the file to the epcs device connected to it. After power-off and then power-on, the fpga will first read the file from the epcs device to configure its own internal static ram, and then it can work normally.
3. The .pof file (program of file), the file is directly downloaded to the external epcs device through the active serial mode of as (active serial), without going through the fpga device. Programs can still be saved after a power failure.
Summary: Method 1 is simple and convenient, but it is not saved when power off. Both methods 2 and 3 can be saved after power off. The difference is that one is indirectly downloaded to the epcs device, and the other is directly downloaded to the epcs device.