what's the difference between the two xilinx constraints

[spriteice]

offset = after valid xilinx

"OFFSET IN BEFORE" and "OFFSET IN AFTER"

Are they functioning exactly the same?

 

[buzkiller]

xilinx offset in before

**broken link removed**



BEFORE defines the relationship between data arrival and the next clock edge. For example, OFFSET IN BEFORE indicates that data will be valid at the input pin of a Xilinx device at a specified time before the next clockedge arrives at the Xilinx device.

AFTER defines the relationship between data arrival and the current clock edge. For example, OFFSET IN AFTER indicates that data will be valid at the input of a Xilinx device at a specified amount of time AFTER the current clock edge on the upstream device.

 

[spriteice]

so can i say actually they have the same function?

for example: assume the period is 30 ns

the following two constraints actually give the same OFFSET constraint.

OFFSET=IN 20.0 BEFORE "CLK"
OFFSET=IN 10.0 after BEFORE "CLK"

am I right?