Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Multicycle Path Exceptions :: Urgent

Hello Altera,

I am basically a Altera competitor user and moved quite recently to Altera Time Quest.

In my Altera design, i need to apply some Multicycle Path exceptions for both -setup and -hold relationship.

Latest competitor tools purely follow Synopsys sdc standard for MCP constraints;

i.e. As per Synopsys sdc specification; the integer value for the -hold argument specifies the number of clock cycles to move the capture edge backward with respect to the default position (relative to the valid setup relationship); the default setting is 0.

For e.g.:

set_multicycle_path -setup 5 -from [get_cells FF1] -to [get_cells FF2]

set_multicycle_path -hold 4 -from [get_cells FF1] -to [get_cells FF2]

To move the capture edge for the hold relationship back to time=0, you need to use set_multicycle_path -hold 4 to move the capture edge back by four clock cycles .

To summarize, Synopsys determines the number of hold cycles as follows:

(hold cycles) = (setup option value) – 1 – (hold option value)

Can you please help me understand if this rule also applies to TimeQuest. ?

Regards,

freak

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    We both follow the Synopsys SDC format. There are some things we both don't support, some things we've probably added in different ways, but anything that matches in naming convention is done the same way. Your analysis is clear and exactly how TimeQuest does it too.