Maximum XOR Toggle rate in a user combinational logic assuming 1024 wide XOR with a depth of 10 levels is as follows:
- 815% - Worst input
- 254% - Random input
Maximum XOR Toggle rate in user combination logic assuming 32 wide XOR with a depth of 5 levels:
- 516% - Worst input
- 114% - Random input
Important: In all the sheets which
do not have a dedicated Clock
Enable column make sure you scale the toggle rate to account
for any signal which gates this logic. For example, if the data toggle rate is modeled
at 50% but the synchronizing clock is enabled 50% of the time, the resulting toggle rate
should be 25% (50% x 50%).
Important: To appreciate what 100% toggle rate means, think of a
constantly enabled toggle flip-flop (TFF) whose data input is tied High. The T-output of
this flip-flop toggles every clock edge. Very few designs could possibly have an average
toggle rate that high (100%).
Note: The I/O sheet has a column to specify signal Data
Rate. Make sure you adjust the Toggle
Rate and Data Rate
columns accurately. For example, on an input signal which toggles on both edges of the
clock you would enter Toggle Rate = 200% and
Data Rate = DDR (Dual Data Rate).