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.

Sign up for GitHub

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

Jump to bottom

Why does PLL define a COMPENSATION value when that is not used? #2341

Open
nelsobe opened this issue Dec 7, 2021 · 1 comment
Open

Why does PLL define a COMPENSATION value when that is not used? #2341

nelsobe opened this issue Dec 7, 2021 · 1 comment

Comments

@nelsobe
Copy link
Contributor

nelsobe commented Dec 7, 2021 •
edited

The techmapper for xc7 https://github.com/SymbiFlow/symbiflow-arch-defs/blob/master/xc/xc7/techmap/cells_map.v defines a default value for COMPENSATION in the PLL advanced module even though it is never used. Should that be removed? Or, is the techmapper incomplete?

@mkurc-ant and @acomodi - can you comment?
@mkurc-ant
Copy link
Collaborator

mkurc-ant commented Dec 8, 2021 •
edited by unfurl-links bot

@nelsobe Hmm, The problem with PLL is that it is not clear which features related to COMPENSATION settings should be emitted for each available choice. As with MMCM there is no one-to-one relation between them.

Currently there are those features in the prjxray database: https://github.com/SymbiFlow/prjxray-db/blob/cd41f08a8a4d2a60053750a0fe10623b1e2e35da/artix7/segbits_cmt_top_r_upper_t.db#L56-L59

I think that to get compensation working we would need to do more "minitests" against vendor tools to identify the correct behavior.

GitHub
Project X-Ray Database: XC7 Series. Contribute to SymbiFlow/prjxray-db development by creating an account on GitHub.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
None yet
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
2 participants
@nelsobe @mkurc-ant