Xilinx ucf constrain notes

ucf constrain

• timing constrain
• input pad to first flip-flop groups
• input offset
• internal flip-flop to flip flop groups
• period
• out flip-flop to output pad groups 
• output offset
• clock
• offset
• duty
• jitter
• rotate
• 90 
• 180
• 270
• multi cycle path
• from one clock dom to another clock dom
• using async fifo to avoid the data missing issue
• data valid
• req fifo.empty/fifo.full
• status
• false path
• not normal paths
• -to
• -from -to
• -through
• -from -through -to 
• data path
• normal paths
• fanout
• set maxfanout
• DCM / DLL/ PLL
• ECO div/mux
• TNM (timing group)
• 
  
• pin assignment constrain
• pad assignment 
• 
  
• slack
• Slack (setup path): =  (requirement - (data path - clock path 
• skew + uncertainty))
• Slack (hold path): = requirement - (clock path skew + uncertainty - data path)