The SLR Crossing by Fanout table shows the fanout of nets that cross between SLRs. It is ordered based on highest fanout first. It gives the following information:
- The total fanout of the net
- Driver cell type
- The SLR load distribution and an indicator of SLR driving region
- The net name
5. SLR Crossings by Fanout
--------------------------
+--------+-------------+------+------+------+------+------------+
| Fanout | Driver Type | SLR0 | SLR1 | SLR2 | SLR3 | Net Name |
+--------+-------------+------+------+------+------+------------+
| 378 | FDRE | 0 | 9* | 369 | 0 | net_name1 |
+--------+-------------+------+------+------+------+------------+
* Indicates driver region
net_name1.When your net has a high fanout, you can experience some difficulty optimizing
for both fanout and SLR crossing. This depends on a combination of the design
structure (for example, whether the net is driven by a register such as FDRE or
FDCE), the timing requirement, and the tool options you select. You can resolve most
issues by increasing the effort levels for place_design and phys_opt_design, and
by using FORCE_MAX_FANOUT properties to further replicate.
Timing penalties incur on every timing path that has the source in one SLR and the load(s) in another. As long as the paths are timed, the challenge increases when more loads are in a different SLR from the driver, compared to a net with the same fanout profile but with most loads placed in the same SLR.
report_timing command. For
example:report_timing -name slr_xing_hfn -through [get_nets net_name1] -setup