RE: [sv-bc] Mantis 1940

Doug,
 
Thanks for the comment.
 
I think that is way beyond the scope of this mantis, which intends to
deal with ambiguities of of use of 'type'. You're welcome to file a new
mantis.
 
I uploaded a new version of the proposal with the correction from your
other mail.
 
Regards,
Shalom


________________________________

	From: Warmke, Doug [mailto:doug_warmke@mentor.com] 
	Sent: Tuesday, October 02, 2007 8:34 PM
	To: Bresticker, Shalom; sv-bc@server.eda.org
	Subject: RE: [sv-bc] Mantis 1940
	
	

	Hi Shalom,

	 

	Observe the following text from the proposal:

	 

	The net data types can represent physical connections between
structural entities, such as gates. A net shall not store a value
(except for the trireg net). Instead, its value shall be determined by
the values of its drivers, such as a continuous assignment or a gate.
See Clause 10 and Clause 27 for definitions of these constructs. If no
driver is connected to a net, its value shall be high-impedance (z)
unless the net is a trireg, in which case it shall hold the previously
driven value.

	 

	The last sentence is a little bit troublesome.

	 

	First, if no driver is connected to a net, it is difficult to
even

	have a previously driven value.  The only way that is possible

	seems to be via a force command.  Perhaps one could imagine

	this text means that something like a bufif0 turned off its
control

	input?  But in that case, I'd still say there was a driver on
the net,

	but it is contributing a high-impedance (z) value.

	 

	Second, in either of those cases above, a trireg will hold a net
at its

	previous logic value, but the strength may change, depending
what

	the previously driven strength was.  Some people might read
"value"

	to mean "combination of logical value + strength".

	 

	I know this came from the existing LRM heritage.  But while
you're at it,

	you might like to clean this up a little bit such that it's
clearer and

	more accurate.

	 

	One possibility would be to replace "value" with "logical value"

	at the tail end of the sentence.  There surely are other
improvements

	to be made as well.

	 

	Thanks,

	Doug

	 

	module top;

	    trireg (medium) t1;

	    trireg (medium) t2;

	    trireg (medium) t3;

	    trireg (medium) t4;

	 

	    reg ctl;

	 

	    bufif1 (weak0, weak1) (t1, 1'b1, ctl);

	    bufif1 (strong0, strong1) (t2, 1'b1, ctl);

	    bufif1 (pull0, pull1) (t3, 1'b1, ctl);

	 

	    initial begin

	        $monitor("%2d: ctl=%0b t1=%v t2=%v t3=%v t4=%v", $time,
ctl, t1, t2, t3, t4);

	        ctl = 1'b1;

	        #10;

	        ctl = 1'b0;

	        force t4 = 1'b1;

	        #10;

	        ctl = 1'b1;

	        release t4;

	        #10;

	    end

	endmodule

	 

	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Bresticker, Shalom
	Sent: Tuesday, October 02, 2007 5:20 AM
	To: sv-bc@server.eda.org
	Subject: [sv-bc] Mantis 1940

	 

	<<1940_D3a.V3.htm>> 
	Hi, 

	I have prepared a new version of Mantis 1940. Please review. 

	Thanks, 
	Shalom 

	Shalom Bresticker 
	Intel Jerusalem LAD DA 
	+972 2 589-6852 
	+972 54 721-1033 

	
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