[sv-ec] Re: [sv-bc] Enum used in concat or assignment pattern

<forwarding bounced email from Greg Jaxon>

-------- Original Message --------
Subject: Re: [sv-bc] Enum  used in concat or assignment pattern
Date: Tue, 02 Jan 2007 11:21:40 -0600
From: Greg Jaxon <Greg.Jaxon@synopsys.com>
To: Moumita Das <moumita@cal.interrasystems.com>
CC: sv-ec <sv-ec@eda-stds.org>, sv-bc <sv-bc@eda-stds.org>

Since it infers the assignment out3=x.b2, it should be just as
erroneous as out3=out4; both assign a byte to a strict SV enum.

Moumita Das wrote:
> Hello,
> 
> According to IEEE std 1800-2005 IEEE standard for System Verilog sec 
> 4.10.3-
> 
> "SystemVerilog enumerated types are strongly typed; thus, a variable of 
> type enum cannot be directly assigned a value that lies outside the 
> enumeration set unless an explicit cast is used or unless the enum 
> vari-able is a member of a union. This is a powerful type-checking aid 
> that prevents users from accidentally assigning nonexistent values to 
> variables of an enumerated type. The enumeration values can still be 
> used as constants in expressions, and the results can be assigned to any 
> variable of a compatible integral type."
> 
> So for the following testcase assignment out3=out4 is an invalid statement.
> So my query is 2nd assignment that is '{out4, out3} =x   is valid or not?
> 
> testcase:
> ------
> 
> typedef enum logic [7:0] {e0, e1} u_t1;
> typedef struct  {byte b1; byte b2;} u_t2;
> 
> module var7(input u_t1 in1, input byte in2);
> wire [8:0] myvar ;
> u_t1 out3;
> byte out4;
> u_t2 x;
> initial
> begin
> out3 = out4;   // This is an error case
> '{out4, out3} =x   ;  //This case is valid or not?
> end
> endmodule
> 
> regards,
> 
> Moumita
> 
> 



-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.