Subject: Re: [sv-bc] left/right justified and patched with zero
From: Dave Rich (David.Rich@synopsys.com)
Date: Wed Nov 05 2003 - 17:35:41 PST
Andy,
First thing I want to say is that SV3.1 now has string data types, so
dealing with characters at the bit level is no longer needed.
Second, the reason fixed-sized data types like byte and int are not
legal has to do with the fact that some Verilog95/2001 simulators allow
you to declare fixed sized data types with a range and then ignore the
range, which is non standard behavior. This type of coding is prevalent
enough that if we allowed packed arrays of fixed sized data types, we
would break existing code. See earlier emails on the reflector that deal
with this issue.
Using a typedef does not remove the problem.
Dave
Andy Tsay wrote:
>Hi,
>
>Thanks for the clarifications that
> 1. Illegal: byte [0:13] pk = "hello world\n";
> 2. Legal, right justified: bit [0:13][0:7] pk = "hello world\n";
> Both pk[0] and pk[1] are filled with 0.
> 3. Legal, left justified: byte unpk [0:13] = "hello world\n";
> Both unpk[12] and unpk[13] are filled with 0.
>
>Shall we consider to make case 1 legal?
>If the follwong is legal, how to fill data to pk2?
> typedef byte BYTE; // make BYTE a type_declaration_identifier
> BYTE [0:13] pk2 = "hello world\n"; // type_decl_id packed_dimension
>
>Thanks,
>Andy
>
>
>--- Arturo Salz <Arturo.Salz@synopsys.com> wrote:
>
>
>>My apologies. Keith is correct.
>>
>> Arturo
>>
>>----- Original Message -----
>>From: "Gover, Keith" <keithg@model.com>
>>To: "Gover, Keith" <keithg@model.com>; "'Arturo Salz'"
>><Arturo.Salz@synopsys.COM>; "Andy Tsay"
>><andytsay@yahoo.com>; "Greg Jaxon" <Greg.Jaxon@synopsys.COM>
>>Cc: <sv-bc@eda.org>
>>Sent: Wednesday, November 05, 2003 12:43 AM
>>Subject: RE: [sv-bc] left/right justified and patched with zero
>>
>>
>>Oops ... wrong cut and paste. Should have been the unpacked array:
>>
>> byte unpk[0:13] = "hello world\n";
>>
>>-Keith
>>
>>--------------------------------------------------------
>>-- Keith Gover
>>-- Technical Marketing Engineer
>>-- Model Technology, Inc.
>>-- office: (503) 685-0896
>>-- mobile: (503) 703-2476
>>-- email: keithg@model.com
>>--------------------------------------------------------
>>------- __@ __@ __@ __@ __~@
>>----- _`\<,_ _`\<,_ _`\<,_ _`\<,_ _`\<,_
>>---- (*)/ (*) (*)/ (*) (*)/ (*) (*)/ (*) (*)/ (*)
>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>"The Only Easy Day was Yesterday!"
>>
>>-----Original Message-----
>>From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org]On Behalf Of
>>Gover, Keith
>>Sent: Wednesday, November 05, 2003 5:40 PM
>>To: 'Arturo Salz'; Andy Tsay; Greg Jaxon
>>Cc: sv-bc@eda.org
>>Subject: RE: [sv-bc] left/right justified and patched with zero
>>
>>
>>Hi Arturo,
>>
>>I think your statement about assignments to unpacked arrays conflicts with
>>what is stated in section
>>2.6. It states:
>>
>> A string literal can be assigned to an unpacked array of characters,
>> and a zero termination is added like in C. If the size differs, it
>> is left justified.
>>
>> byte c3 [0:12] = "hello world\n" ;
>>
>>Therefore the assignment in Andy's example should be legal:
>>
>> byte [0:13] pk = "hello world\n";
>>
>>-Keith
>>
>>--------------------------------------------------------
>>-- Keith Gover
>>-- Technical Marketing Engineer
>>-- Model Technology, Inc.
>>-- office: (503) 685-0896
>>-- mobile: (503) 703-2476
>>-- email: keithg@model.com
>>--------------------------------------------------------
>>------- __@ __@ __@ __@ __~@
>>----- _`\<,_ _`\<,_ _`\<,_ _`\<,_ _`\<,_
>>---- (*)/ (*) (*)/ (*) (*)/ (*) (*)/ (*) (*)/ (*)
>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>"The Only Easy Day was Yesterday!"
>>
>>-----Original Message-----
>>From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org]On Behalf Of
>>Arturo Salz
>>Sent: Wednesday, November 05, 2003 5:16 PM
>>To: Andy Tsay; Greg Jaxon
>>Cc: sv-bc@eda.org
>>Subject: Re: [sv-bc] left/right justified and patched with zero
>>
>>
>>Andy,
>>
>>The declaration "byte [0:13] pk " is illegal.
>>Packed arrays can only be made of the single bit types (bit, logic, reg,
>>wire,...).
>>The legal version of what I believe you want is:
>> bit [0:13][0:7] pk = "hello world\n";
>>And then
>> pk[0] is 0
>> pk[1] is 0
>> ...
>> pk[12] is "d"
>> pk[13] is "\n"
>>
>>The declaration "byte unpk[0:13]" is legal, but the assignment is illegal.
>>You could do the following:
>> byte unpk[0:13] = { "h", "e", "l", "l", ... "d", 0, 0 };
>>But then the sizes have to match, which is why I added 0,0 at the end.
>>
>> Arturo
>>
>>----- Original Message -----
>>From: "Andy Tsay" <andytsay@yahoo.com>
>>To: "Greg Jaxon" <Greg.Jaxon@synopsys.COM>
>>Cc: <sv-bc@eda.org>
>>Sent: Monday, November 03, 2003 5:13 PM
>>Subject: Re: [sv-bc] left/right justified and patched with zero
>>
>>
>>Hi,
>>
>>Let me try to put it in another way.
>>For the following examples:
>> byte unpk[0:13] = "hello world\n";
>> byte [0:13] pk = "hello world\n";
>>
>>What are the values for unpk[12], unpk[13], pk[0], and pk[1]?
>>
>>Thanks,
>>Andy
>>
>>--- Greg Jaxon <Greg.Jaxon@synopsys.com> wrote:
>>
>>
>>>Andy Tsay wrote:
>>>
>>>
>>>
>>>> byte unpk[0:13] = "hello world\n";
>>>> // same as unpk = {"hello world\n",8'b0, 8'b0}; ???
>>>>
>>>>
>>>Please ask this in the form
>>>
>>> // same as unpk = "hello world\n\0\0"; ???
>>>
>>>Since as posed it yields a length error trying to put three things into
>>>and array of 14 things.
>>>
>>>Greg Jaxon
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>
-- -- David.Rich@Synopsys.com Technical Marketing Consultant http://www.SystemVerilog.org tele: 650-584-4026 cell: 510-589-2625
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