<promach3>
Yosys has only limited support for tri-state logic at the moment. (cells_sim.v:401)
<promach3>
Lofty: smt2: ERROR: Unsupported or unknown directionality on port B of cell ddr3_memory_controller.BB_dqs_n (TRELLIS_IO).
<Lofty>
Then evidently you can't have inout ports in SBY, so you'll need to figure out a way of removing the input buffers
<promach3>
what ?
<promach3>
why remove buffer ?
<promach3>
I need tristate for DDR3 RAM application
<promach3>
Lofty:
<Lofty>
As I mentioned
<Lofty>
You can't have inout ports
<Lofty>
So you can't have tristate buffers
<promach3>
thus yosys gave warnings about limited support for tri-state logic
<Lofty>
Yosys does kinda accept tristate logic
<Lofty>
But in this case, it's not really relevant
<promach3>
but why it failed in my situation ?
<promach3>
ok, I suppose yosys formal engine does not yet support tri-state logic
<promach3>
Lofty:
<Lofty>
Well, no
<promach3>
did I conclude it correctly ?
<Lofty>
In this case, the error is coming from the Yosys smt2 backend
<Lofty>
Where I'm assuming an inout is unrepresentable
<promach3>
smt2 is related to formal
<Lofty>
Yes, I'm assuming it's a file format
<promach3>
ok
<promach3>
so, how do I work around this situation ?
<promach3>
Lofty:
<Lofty>
... remove the buffers
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<Lofty>
Like I said
<promach3>
DDR3 require tri-state buffers
<promach3>
cannot remove tri-state logic
<Lofty>
Yes, but in a formal context you don't need them
<promach3>
ok, I see
<promach3>
let me think how to represent tri-state for formal
<Lofty>
Well, you can't.
<promach3>
Lofty: so, maybe I could assume(some values) for the input direction ?
<Lofty>
if (direction) assert(output condition) else assert(input condition)
<Lofty>
Or something
<promach3>
cool
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<cr1901_modern>
mwk: Re: the VPR mode in my machxo2 PR... it has become clear talking to symbiflow folks that I didn't actually understand the purpose of the code I was copying, so... oops on my end :P. In the next round of PR, I will remove the VPR mode