Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Determine frequency of Cyclone V clock #655

Open
Lunaphied opened this issue Dec 13, 2021 · 3 comments
Open

Determine frequency of Cyclone V clock #655

Lunaphied opened this issue Dec 13, 2021 · 3 comments

Comments

@Lunaphied
Copy link
Contributor

This needs to actually be measured on real hardware, value is not well documented.

@whitequark
Copy link
Member

The Cyclone-V handbook says:

If you use the internal oscillator, you can choose a 12.5, 25, 50, or 100 MHz clock under the Device and Pin Options
dialog box, in the Configuration page of the Intel Quartus Prime software.

It's not entirely clear where this adds a divider in the clocking path, so this needs to be checked.

@Ravenslofty
Copy link
Contributor

Ravenslofty commented Dec 13, 2021

The setting in question controls set_global_assignment -name ACTIVE_SERIAL_CLOCK FREQ_{100,50,25,12_5}MHZ, which I think controls the oscillator frequency when loading bitstreams from flash.

More specifically: it changes the OPTION_REG_EXTERNAL_CLK_SPI part of bitstream Option RAM to 001 (100MHz) / 011 (50MHz) / 101 (25MHz) / 111 (12.5MHz). (this has been added to Mistral, since it was overlooked)

I think one would need to manually instantiate a cyclonev_oscillator block.

@Ravenslofty
Copy link
Contributor

It seems that AN 496 documents the Cyclone V internal oscillator at 100 MHz maximum. This is... still incredibly vague but it's better than nothing.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Development

No branches or pull requests

3 participants