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nikhil_h
Visitor
Visitor
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Registered: ‎02-18-2020

Placement issue with control sets

Hi,

Please let me know how to resolve the placement issue for the below error, 

ERROR: [Place 30-487] The packing of instances into the device could not be obeyed. There are a total of 19650 slices in the device, of which 14382 slices are available, however, the unplaced instances require 14697 slices. Please analyze your design to determine if the number of LUTs, FFs, and/or control sets can be reduced.

Number of control sets and instances constrained to the design
Control sets: 6248
Luts: 56117 (combined) 68369 (total), available capacity: 78600
Flip flops: 98712, available capacity: 157200
NOTE: each slice can only accommodate 1 unique control set so FFs cannot be packed to fully fill every slice

 

-currently, I am using zynq 7030 board, 

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joancab
Teacher
Teacher
285 Views
Registered: ‎05-11-2015

- Optimize your design

- Reduce the size of your design

- Go for a bigger device

Even if you find a way to fit your design, because you are using ~90% of it, you will have problems every time you change the slightest thing.

It's wise not to use more than ~75% of an FPGA resources.

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Registered: ‎01-22-2015

@nikhil_h 

A control set is a specific grouping of control signals (set/reset, clock enable and clock).  Two FFs that use the same control set can be placed in the same FPGA slice.  However, two FFs that use different control sets must be placed in different slices.  In the ZYNQ 7030, a slice contains eight FFs.

So, reducing the number of unique control sets in your design can result in more efficient use of FPGA resources (eg. FFs can be packed to fully fill every slice).   

For more information on controls sets and on reducing the number of control sets see pg49 of UG949(v2020.2).  Also, search UG904 for "control sets" and you will find implementation strategies that help you reduce the number of unique control sets.

Cheers,
Mark

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