Sometimes the FF cell might be initialized during the map process, e.g.
some FPGA platforms (Anlogic Eagle and Lattice ECP5 for example) has
only a "SR" pin for a FF for async reset, that resets the FF to the
initial value, which means the async reset value should be set as the
initial value. In this case the DFFINIT pass shouldn't reinitialize it
to a different value, which will lead to error.
Add a "-noreinit" parameter for the safeguard. If a FF is not
technically initialized before DFFINIT pass, the default value should be
set to x.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
On some platforms the string to initialize DFF might not be "high" and
"low", e.g. with Anlogic TD it's "SET" and "RESET".
Add a "-strinit" parameter for dffinit to allow specify the strings used
for high and low.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
The MSLICEs on the Eagle series of FPGA can be configured as Distributed
RAM.
Enable to synthesis to DRAM.
As the Anlogic software suite doesn't support any 'bx to exist in the
initializtion data of DRAM, do not enable the initialization support of
the inferred DRAM.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
This reverts commit 43030db5ff.
For a synthesis tool, generating EG_LOGIC cells are a good choice, as
they can be furtherly optimized when PnR, although sometimes EG_LOGIC is
not as blackbox as EG_PHY cells (because the latter is more close to the
hardware implementation).
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
In some cases the memory_bram pass shuffles the order of the bits in a
memory's RD_DATA port. Although the order of the bits in the WR_DATA and
WR_EN ports is changed to match the RD_DATA port, the order of the bits
in the initialization data is not.
This causes reads of initialized memories to return invalid data (until
the initialization data is overwritten).
This commit fixes the bug by shuffling the initdata bits in exactly the
same order as the RD_DATA/WR_DATA/WR_EN bits.
This is useful if you want to place FF manually ... can't merge SR in those
because it might make the manual placement invalid
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
In an initial statement, blocking assignments are normally used
and e.g. verilator throws a warning if non-blocking ones are used.
Yosys cannot however properly resolve the interdependencies if
blocking assignments are used in the initialization of SB_RAM_40_4K
and thus this has been used.
This patch will change to use non-blocking assignments only for yosys
Icenowy Zheng
Clifford Wolf
whitequark
Sylvain Munaut
David Shah
Graham Edgecombe
David Shah
Olof Kindgren