RE: [sv-bc] streaming operator unpack doubt

'If the source expression contains more bits than are needed, the
appropriate number of bits shall be consumed from its left (most
significant) end."

I believe 'its' is referring to the source expression, before
re-ordering. After re-ordering is no longer the source expression.

Dave Rich
Verification Technologist
Mentor Graphics Corporation
New Office Number: 510-354-7439

  <http://www.twitter.com/dave_59> <http://go.mentor.com/drich>

From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
Steven Sharp
Sent: Thursday, February 10, 2011 4:51 PM
To: Arturo Salz; Daniel Mlynek; sv-bc@eda.org
Subject: RE: [sv-bc] streaming operator unpack doubt

Actually, I think he meant "reg [3:1] c", since he is talking about the
truncation case, and his suggested results are 3 bits wide.

The LRM specifies that the most significant bits are taken. But when
the streaming operator specifies some kind of reordering of the stream,
are those the most significant bits of the source expression before
reordering, or after? That is his question.

        
________________________________

        From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf
Of Arturo Salz
        Sent: Thursday, February 10, 2011 3:20 PM
        To: Daniel Mlynek; sv-bc@eda.org
        Subject: RE: [sv-bc] streaming operator unpack doubt

        Daniel,

        I assume in you meant "reg [5:1] c;" in your code snippet.

        The sentence following the one you quoted in the LRM states:
However, if more bits are needed than are provided by the source
expression, an error shall be generated.

        An the example that follows reinforces the concept:

        {>>{ a, b, c }} = 23'b1; // error: too few bits in stream

        Hence, in your example, an error should be generated.

                        Arturo

        From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf
Of Daniel Mlynek
        Sent: Thursday, February 10, 2011 4:59 AM
        To: sv-bc@eda.org
        Subject: [sv-bc] streaming operator unpack doubt

        What should be the results of streaming operator unpack if there
is more than we need bits on RHS
        LRM:
        'If the source expression contains more bits than are needed,
the appropriate number of bits shall be consumed from its left (most
significant) end."
        But does LRM mean that we need to take appropriate number of
bits from source expression or from reordered stream.
        So attached example should print:

        1z0
        0z1

        or

        1z0
        x0z

        Example

        module top;
        reg [4:1] b1;
        reg [5:1] d;
        initial
        begin
            #1 b1='b1z0x;
              {>>{c}} =b1; $display("c=%b ",c);
            #1 b1='b1z0x;
              {<<{c}} =b1; $display("c=%b ",c);
        end
        endmodule

        DANiel

        
        
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