0000609: 16.14 confusing meaning of ##cycle with clocking drive

EDA.org Mantis

Viewing Issue Simple Details [ Jump to Notes ] [ Wiki ]

[ View Advanced ] [ Issue History ] [ Print ]

Category

Severity

Date Submitted

Last Update

0000609

[SystemVerilog P1800] SV-EC

minor

2005-03-24 11:49

2007-04-06 11:10

Reporter

Steven Sharp

View Status

public

Assigned To

Arturo Salz

Priority

normal

Resolution

open

Status

closed

Product Version

Summary

0000609: 16.14 confusing meaning of ##cycle with clocking drive

Description

I am filing this erratum for another reviewer:

The special semantics of ##cycle as defined by section 15.14 on page 191 we believe are going to confuse the end user. Part of this is a result of using the same operator as an nonblocking assignment (NBA) normally would, but more importantly is the semantic selection based on the object on the LHS of the clocking drive.

Essentially, we have overloaded the meaning of the cycle delay operator to choose a different clocking block under certain circumstances. Since users are unlikely to have multiple clocking blocks when they first encounter they are unlikely to expect it to select a different clocking block than the default one. This is especially true as section 16.10 in the LRM makes no mention of the fact that the ## operator may select a different clocking block if the cycle delay is being used with a clocking drive rather than with a normal NBA.

We would recommend removing this special semantic for clocking drives, but if necessary creating a semantic wherein the user could specify which clocking block as part of their ## operator. For example, we could take a page from the use of #1ns and have the user optionally be able to specify ##5block2 where block2 would be the clocking block they want to use for the 5 cycles specified.

Given all the issues with clocking drives, one begins to wonder if perhaps it is not better to simply eliminate it as a concept and allow normal assignment operators to modify the clocking output variable variables.

Additional Information

Closed on Mar/5/2007. unanimously. Covered by 0000890.
Updated Status/CLOSED

Tags

No tags attached.

Type

Errata

Attached Files

Relationships

Notes
(0003580) mehdi_mohtashemi (manager) 2007-04-06 11:10	Closed on Mar/5/2007. unanimously. Covered by mantis 890.

Issue History
Date Modified	Username	Field	Change
2005-03-24 11:49	Steven Sharp	New Issue
2005-03-24 11:49	Steven Sharp	Type	=> Errata
2005-04-19 20:59	Brad Pierce	Status	new => assigned
2005-04-19 20:59	Brad Pierce	Assigned To	=> Arturo Salz
2007-04-06 11:10	mehdi_mohtashemi	Note Added: 0003580
2007-04-06 11:10	mehdi_mohtashemi	Status	assigned => closed
2007-04-06 11:10	mehdi_mohtashemi	Additional Information Updated

Mantis 1.1.7[^]