Ignore the timing path from the current DMA address to the register map,
this is just a debug signal at the moment.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
If the internal FIFO is larger than one block ram there will be multiple
BRAMs called ram_reg[0], ram_reg[1]. Modify the BRAM constraint rule so that
it matches these as well.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
We really only want to apply the CDC constraints if the clocks are actually
asynchronous. Unfortunately we can't use if ... inside a xdc script. But we
can use expr which has support for a ? b : c if-like expression. We can use
that to create helper variables that contains valid clock when the clock
domains are asynchronous or {} if they are not. Passing {} as
set_false_path/set_max_delay as either the source or destination will cause
it to abort and no constraints will be added.
Also add -quiet parameters to avoid generating warning if the constraints
could not be added.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
All the FPGA internal control signals are active high, using a active low
reset inserts a extra invert LUT. By using a active high reset we can avoid
that.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Instead of just marking all clock domains as asynchronous set the
appropriate constraints for each CDC path.
For single-bit synchronizers use set_false_path to not constraint the path
at at all.
For multi-bit synchronizers as used for gray counters use set_max_delay with
the source clock period domain to make sure that the signal skew will not
exceed one clock period. Otherwise one bit might overtake another and the
synchronizer no longer works correctly.
For multi-bit synchronizers implemented with hold registers use
set_max_delay with the target clock period to make sure that the skew does
not get to large, otherwise we might violate setup and hold time.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Lars-Peter Clausen
Adrian Costina
Rejeesh Kutty
Istvan Csomortani