RE: What does 'last_event really return?

Arpad,

Thanks for raising the issue in our book. You're right that we overlooked
the real-valued form of the 'last_event attribute. My aplogies for that.
Note that, curiously, VHDL-AMS does not also define a real-valued form of
the 'last_active attribute, only the TIME-valued form from VHDL.

Cheers,

PA

--
Dr. Peter J. Ashenden                peter@ashenden.com.au
Ashenden Designs Pty. Ltd.           www.ashenden.com.au
PO Box 640                           VoIP: 0871270078@sip.internode.on.net
Stirling, SA 5152                    Phone (mobile):  +61 414 709 106
Australia

> -----Original Message-----
> From: owner-vhdl-ams@eda.org [mailto:owner-vhdl-ams@eda.org] 
> On Behalf Of Muranyi, Arpad
> Sent: Thursday, 16 February 2006 06:37
> To: vhdl-ams@eda.org
> Subject: RE: What does 'last_event really return?
> 
> 
> Ernst,
> 
> Thank you very much for the clarification,
> this explains it very well!  So a tool
> claiming to be "VHDL-AMS" should support
> the syntax without the explicit conversion,
> correct?
> 
> This brings up another question about Peter
> Ashenden's book.  The tables on p. 144 and
> p. 674 indicate that the return type of
> S'last_event is time.  Considering that the
> title of the book is "The System Designer's
> Guide to VHDL-AMS" (and not VHDL), is this
> a typo in the book?
> 
> Thanks,
> 
> Arpad
> =========================================== 
> 
> -----Original Message-----
> From: Ernst Christen [mailto:Ernst.Christen@synopsys.COM] 
> Sent: Wednesday, February 15, 2006 11:50 AM
> To: Muranyi, Arpad; vhdl-ams@eda.org
> Subject: Re: What does 'last_event really return?
> 
> Hi Arpad,
> 
> I believe the answer to your question is related to the VHDL 
> language version supported by 
> your tool. 
> 
> The VHDL language, defined by IEEE Std. 1076, defines 
> S'LAST_EVENT to be a function whose 
> result type is the predefined type TIME. All tools compliant 
> with any version of VHDL will 
> support this function. 
> 
> VHDL-AMS, defined by IEEE Std. 1076.1, is an extension of 
> VHDL and as such supports 
> everything defined in VHDL (currently the 1993 version). 
> VHDL-AMS defines another function 
> S'LAST_EVENT whose result type is the predefined type REAL. 
> All tools supporting VHDL-AMS 
> will support this function, but tools supporting the base 
> language will not.
> 
> In the case of VHDL-AMS, the two overloaded functions are 
> disambiguated based on their 
> signature, which for the S'LAST_EVENT function in essence 
> means its result type. In your 
> example, you are looking for a function whose return type is 
> REAL. This function is only 
> available in tools compliant with VHDL-AMS. Your second 
> attempt, based on TIME'Pos, will 
> always force the version of S'LAST_EVENT returning TIME to be 
> called, so it is expected to 
> work in all tools.
>