create_generated_clock question

[ymiler]

Hi

following template of create_generated_clock constraint:

create_generated_clock -name {<constraint name>} [get_pins {<pin name>}] -source [get_pins {<opin name>}] -divide_by {1} -multiply_by {1} -add -master_clock [get_clocks {cnvr_fpga_bt_clk_switch_out}]

What is the meaning of -master_clock [get_clocks {<clock name>}] in the create_generated_clock constraint?

Why do we need add it ? what it the function of this command ?

[ShengN_Intel]

Hi,

That -master_clock <clock> is to specify the clock of the source node check this link https://www.intel.com/content/www/us/en/docs/programmable/683432/22-1/tcl_pkg_sdc_ver_1-5_cmd_create_generated_clock.html

Thanks,

Regards,

Sheng

[sstrell]

If there is the possibility of multiple clocks at the source node specified (perhaps through the use of -add), -master_clock lets you pick which clock to use as the source for this generated clock.

[ymiler]

OK

If there is only 1 source clock , I shouldn't add the flag -master_clock

Thank you 

[sstrell]

No, it's not needed.