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diannaoyoujian
Contributor
Contributor
235 Views
Registered: ‎02-28-2019

mmcm clocks

Hi,

I have two question about MMCM on zcu102。

(1)I set “no buffer” for clk_out1(as shown in picture BUFGCE1),but afer synthesis, there are still BUFGCE(as shown in picture BUFGCE2)。Why?

(2)I use two MMCM。MMCM0 gen clk_out2,then clk_out2 is input for MMCM2(as shown in picture PLACE1).But there is error in place stage(as shown in picture PLACE2).Why?How can i resolve it?

BR!

BUFGCE1.png
BUFGCE2.png
PLACE1.png
PLACE2.png
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1 Reply
hongh
Moderator
Moderator
195 Views
Registered: ‎11-04-2010

1. When you set “no buffer” for clk_out1, then no BUFG will be instantiated in the IP. But the synthesis tool will evaluate the path and insert BUFG automatically if the tool thinks necessary.

2. The error just reminds you that such connection cannot use the dedicated clock routing path. You can add the constraint in the error message into your XDC to downgrade the error to warning. If the timing requirement can be fulfilled, the design can still work properly.

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