theUltimateSource
Junior Member level 1
hello,
Vivado cannot close timing between two clocks, "vid_io_in_clk" and "vid_io_out_clk". Both IP cores have been configured for assynchronous buffering. I was expecting that the IP core are including constraints to declare the clocks between the data path as mutually exclusive (which is what I want them to be).
Vivado tries to meet timing with all clocks, which is default behaviour. Now I have 2 options:
(A) declare "vid_io_in_clk" as assynchronous to "aclk" and "aclk" to "vid_io_out_clk"
(B) declare "vid_io_in_clk" and "vid_io_out_clk" as assynchronous, which is what Vivado is complaining about
(A) seems more correct to me than (B). I think with (A) Vivado should no longer see a clock relation for (B). But CDC's for (A) are black boxes, so what about control signals like handshaking and watermarks, these are not assynchronous and I cannot constrain them.
P.S. sorry for the image I don't know why it's so tiny
- - - Updated - - -
Ok, I see now that (A) has multicycle constraints. I think I can treat (B) as completely assynchronous then, as long as (A) meets timing. Is this correct?
Vivado cannot close timing between two clocks, "vid_io_in_clk" and "vid_io_out_clk". Both IP cores have been configured for assynchronous buffering. I was expecting that the IP core are including constraints to declare the clocks between the data path as mutually exclusive (which is what I want them to be).
Vivado tries to meet timing with all clocks, which is default behaviour. Now I have 2 options:
(A) declare "vid_io_in_clk" as assynchronous to "aclk" and "aclk" to "vid_io_out_clk"
(B) declare "vid_io_in_clk" and "vid_io_out_clk" as assynchronous, which is what Vivado is complaining about
(A) seems more correct to me than (B). I think with (A) Vivado should no longer see a clock relation for (B). But CDC's for (A) are black boxes, so what about control signals like handshaking and watermarks, these are not assynchronous and I cannot constrain them.
P.S. sorry for the image I don't know why it's so tiny
- - - Updated - - -
CDC's for (A) are black boxes, so what about control signals like handshaking and watermarks, these are not assynchronous and I cannot constrain them.
Ok, I see now that (A) has multicycle constraints. I think I can treat (B) as completely assynchronous then, as long as (A) meets timing. Is this correct?