Hello. My name is Ume Onigiri.
Last time I was able to reduce the configuration time in FPP mode compared to AS mode.
However, it seems that there is still a way to shorten the time from powering on the device to user mode.
The process from power-on to user mode is as follows.
So far, we have only reduced the time required for configuration.
This time, we will shorten the time required for Power On Reset and initialization.
Power On Reset (POR)
For more information on POR, please refer to the article written by one of our predecessors. As described in his article, POR has two modes, "Standard" and "Fast".
The time required for POR is different in each mode.
Standard: 50 to 200 ms
Fast: 3 to 9 ms
Ume Onigiri thought that if you can finish POR quickly, you should choose Fast in any case.
However, in Fast, the power supplies must be brought up to the recommended voltage as soon as possible.
In Standard mode, the power supplies must be brought up to the recommended voltage by 50ms after power-on, whereas in Fast mode, they must be brought up to the recommended voltage by 3ms.
Note that the restrictions on power-up are more severe when using POR in Fast mode.
The POR mode setting can be changed by processing the msel pin.
Also, some configuration modes may limit the mode of POR.
For example, in the FPP mode of Cyclone® IV E, the only POR mode that can be selected is Fast.
Initialization
Please refer to the article on initialization written by one of our senior members.
As mentioned in his article, there are two types of clock sources for initialization: internal oscillator and external clock.
By default, the internal oscillator is used, and the user mode is entered after 3192 clock cycles.
The internal oscillator has a maximum frequency of 40 MHz.
The frequency may vary slightly.
The external clock allows a maximum of 40 MHz clock input from the CLKUSR pin.
Therefore, by using a stable 40 MHz clock from an external source, the initialization time can be shortened somewhat compared to when using an internal oscillator.
How to set CLKUSR is also described in the article of my predecessor.
Conclusion
The time it takes for a device to start up is affected not only by the configuration time but also by the POR time and initialization time.
To shorten device start-up time, please consider POR time and initialization time.
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