set_max_skew giving path not found warning

Hi Syafieq,

I was following the guidelines in the article you shared.

I created a clock group with only the spi clk and spi virtual clock

# Create clock group for SPI clk
set_clock_groups -asynchronous -group [get_clocks {spi_clk spi_virt_clk}]

Then i created the net delay and max skew constraints

# Set net delay between spiclk to sys clk data crossings

set_net_delay -from [get_registers {*spi*shift_reg[*]*}] -to [get_registers {*spi*rx_data_reg[*]*}] -max -get_value_from_clock_period dst_clock_period -value_multiplier 0.8

# Set max skew between spiclk to sys clk data crossings

set_max_skew -from [get_registers {*spi*shift_reg[*]*}] -to [get_registers {*spi*rx_data_reg[*]*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.8

Only the max skew command generated warning. The net delay command using the same search keywords found the path.

Warning (332182): No path is found satisfying assignment "set_max_skew -from [get_registers {*spi*shift_reg[*]*}] -to [get_registers {*spi*rx_data_reg[*]*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.800 ". This assignment will be ignored.
Info (286030): Timing-Driven Synthesis is running
Warning (332182): No path is found satisfying assignment "set_max_skew -from [get_registers {*spi*shift_reg[*]*}] -to [get_registers {*spi*rx_data_reg[*]*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.800 ". This assignment will be ignored.
Warning (332182): No path is found satisfying assignment "set_max_skew -from [get_registers {*spi*shift_reg[*]*}] -to [get_registers {*spi*rx_data_reg[*]*}] -get_skew_value_from_clock_period min_clock_period -skew_value_multiplier 0.800 ". This assignment will be ignored.

I tried by commenting out only the clock group command. Then the max skew and net delay commands gave no warnings.

The net delay command works and doesnt generate a warning.

If i comment out the set_clock_group command then the max_skew command executes and doesn't generate a warning.

I also tried to use the name finder as you suggested to see the response. I get an error showing that, first create timing netlist must be run. I think in the normal compilation flow, the sdc are executed after the netlist is created. so this command should work as it does for other commands.

In the TA, I am able to see the registers using the get registers command:

Regards

Jay