Hello, I'm Hachi.
In the last installment of "Choosing a Configuration ROM", you learned about configuration modes and why you should configure in AS mode.
This time, I would like to think about how long it takes from the start to the end of configuration when configuring in AS mode.

As we learned last time, AS mode reads data from EPCS. It has been found to be device dependent with respect to configuration data size.

　　　For EP4CE10: rbf file size = 2,944,088bits

So, at what clock frequency are you transferring data?
First, I decided to check the AS mode connection diagram in the handbook to find out about the clock.
(found in the Cyclone® IV Device Handbook under System Integration → Configuration → AS Configuration)

The clock supplied from the FPGA to the EPCS was named DCLK, so I searched the handbook and found that it was described in the following places.
Data Sheet → Switching Characteristic → Core Performance Configuration JTAG Specification

You can see that DCLK in AS mode is a fixed value. DCLK was 20 MHz or 40 MHz.

Now, how do we calculate the configuration time from here...
As I read through the handbook, I found a formula for calculating the configuration time!

I calculated the configuration time using the formula above.

However, this is only a reference value.
Below is a summary of the approximate configuration time in Cyclone® IV E AS mode.
As you can see, the time required for configuration is proportional to the logic scale.

Now you know how long it takes to configure.

When I explained it to my seniors, they said, "...it's not enough."
It seems that some steps other than data transfer are executed before the user logic starts working after turning on the power.

In the world of seconds, it seems that the user logic starts working immediately after the power is turned on, but implementation goes through various processes.
Next time, we will study steps other than data transfer!