Wednesday, 2019-07-03

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promachZipCPU: hmm... poor man sequence method in your article does not help much in this case01:24
promachit seems like the poor man method might not be able to achieve what I try to achieve01:26
promachwait, it is doable01:31
promachFor , why is line 27 executed ?02:10
tpbTitle: D flip-flop with asynchronous reset · GitHub (at
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ZipCPUpromach: That's the same thing I've been explaining to you for days.  Because the asynchronous reset is assumed to be dropped just before the clock edge.  The two are race conditions against each other.10:24
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promachZipCPU: so, enable signal is actually high during posedge clk ?13:42
ZipCPU"<ZipCPU> promach: That's the same thing I've been explaining to you for days.  Because the asynchronous reset is assumed to be dropped just before the clock edge.  The two are race conditions against each other."13:43
promachI saw that13:43
promachin the online log13:43
promachZipCPU: so, enable signal is actually high during posedge clk ?13:43
promachotherwise line 27 will not be executed13:44
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promachZipCPU: manipulating the enable signal input will also not solve such issue13:59
promachI am afraid13:59
promachthis is a delta race condition13:59
promachdo I need to extend the enable signal ?13:59
promachas well as the reset signal ?14:00
ZipCPUif (reset) assume(!enable)14:00
promachif (reset_wsync) assume(!enable)14:01
promachbecause of  always_ff @(posedge write_clk, posedge reset_wsync)14:02
promachbut this is not reliable since this is nly for formal verification14:02
promachand we only do it after the reset synchronizer14:02
promachZipCPU: this is a bit tricky to solve14:03
promachAs for "if (reset) assume(!enable)" , this is not helpful too since we could have vastly different clocks speed14:05
promachthis is why we have afifo instead of cheap, conventional synchronizer pair14:06
promachZipCPU: what do you think ?14:06
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bwidawskso would anyone be opposed to having yosys catch SIGINT and ignoring it when in interactive mode?18:05
bwidawskI'd be happy to write the patch18:05
ZirconiumXMaybe post an RFC issue in GitHub18:06
ZirconiumXI have something I'd like to add to Yosys, too, since it seems to be a common enough idiom18:07
bwidawskZirconiumX› okay, writing the RFC now18:07
ZirconiumX(namely, adding a parameter to the $pos cell to round the output width to a given multiple of N)18:08
ZirconiumX(which I'm sure daveshah would like)18:08
tpbTitle: RFC: Ignore SIGINT in interactive mode · Issue #1157 · YosysHQ/yosys · GitHub (at
ZirconiumXbwidawsk: 👍18:15
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bwidawskwould also be nice if long output invoked the pager18:33
ZipCPUWhy not just use "tee" to send it to a file you can then run the pager on?18:36
tntbwidawsk: sigint is ctrl-c right ?  why ignore it ?18:42
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ZirconiumXtnt: in interactive mode18:46
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tntZirconiumX: yeah, I got that, but I still want to easily kill yosys (or at the very least the running command).18:47
tntZirconiumX: like ... when yosys mis-understood a ram inferrance and starts generating millions of FFs ...18:48
ZirconiumXThen we can make ^C while executing a command abort it, perhaps?18:48
ZirconiumXI'm not sure if the current architecture of Yosys permits that though18:49
tntsure, that'd be fine (even better than killall), but no idea how easy / hard it'd be ...18:49
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tntlongjmp :p18:49
ZirconiumXI'd actually use threading here, I think18:49
ZirconiumXRunning a command spawns a thread to execute it18:50
daveshahYou'd have to have the command operate on a copy of the netlist structure then18:51
daveshahOtherwise things would be inconsistent when you terminated the command18:51
daveshahAnd that would significantly increase memory usage on some big designs (where the netlist can be several GB)18:52
ZirconiumXI don't think setjmp/longjmp would be much better in that instance18:53
ZirconiumXdaveshah: actually, couldn't you get away with copy-on-write here?19:04
ZirconiumXIt might not be ideal, but it would be consistent19:05
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