Achronix Synthesis - Manual (Page 14)

14 UG018, April 15, 2013
Figure 7- Replicated High Fan-in State Example
Both state machines in the above Figure 7 are equivalent in function, but State A is duplicated
in Version II so that A and A1 have two or less return inputs. As a result, if each state has to
deal with two additional inputs, they can now be contained in one 4‐input LUT. Although this
example is si
mplistic, the methodology can be applied to larger and more complex state
machines.
Fanout Limit:
This fanout limit can also be controller through RTL design. In this case if the user knows
about a net with a high fanout and wants to replicate the cell after a certain fanout is reached,
the following coding style is needed:
wire net1 /* synthesis syn_maxfan = 8 */ ;
Here Synplify Pro will infer a buffer/logic if the fanout limit of the net “net1” exceeds 8.