(r12) LCS2016_070 < P1076

P1076 Web>VHDL2017>LCS2016_070 (revision 12) (raw view)~~EditAttach~~
---+ Language Change Specification for Bidirectional Connections
---++ 

| <sticky><b>LCS Number:</b></sticky> | LCS-2016-070 |
| <sticky><b>Version:</b>   </sticky> | 3 |
| <sticky><b>Date:</b>      </sticky> | 26-Mar-2017  |
| <sticky><b>Status:</b>    </sticky> | Voting |
| <sticky><b>Author:</b>    </sticky> | Patrick Lehmann %BR% Martin Zabel |
| <sticky><b>Email:</b>     </sticky> | [[Main.PatrickLehmann]] %BR% [[Main.MartinZabel]] |
| <sticky><b>Source Doc:</b></sticky> | [[BidirectionalConnections][Bidirectional Connections]] |
| <sticky><b>History Doc:</b></sticky> | [[LCS2016_070_History ]] |
| <sticky><b>Summary:</b>   </sticky> | Adds bidirectional connections aka. Spaceship assignments. |

<noautolink>
<sticky>
Changes are shown in %RED%red font%ENDCOLOR%.%BR%
Deletions are %RED%<del>crossed out</del>%ENDCOLOR%.%BR%
Restructuring is shown in crossed out %GRAY%<del>gray font%ENDCOLOR% somewhere else in %GRAY%gray font%ENDCOLOR%.%BR%
Editing or reviewing notes in %GREEN%green font%ENDCOLOR%.
 

---++ Details of Language Change
---+++ (070.1) 6.4.2.3 Signal declarations
%GREEN%[Editor note: 1st paragraph on page 69]%ENDCOLOR%

A signal may have one or more <i>sources</i>. For a signal of a scalar type, %RED%the set of sources is the union of the subset of primary sources and of %BR%
the subset of secondary sources. %GRAY%<del>each source is either a driver (see 14.7.2) or an *out*, *inout*, *buffer*, or *linkage* port of a component instance %BR%
or of a block statement with which the signal is associated.</del>%ENDCOLOR% The subsets are determined as follows:%ENDCOLOR%
   * icon:line_lr %RED%For a signal of a scalar type,%ENDCOLOR% %GRAY%each%ENDCOLOR% <i>%RED%primary%ENDCOLOR% %GRAY%source%ENDCOLOR%</i>
       %GRAY%is either a driver (see 14.7.2) or an *out*, *inout*, *buffer*, or *linkage* port of a component %BR%
     instance or of a block statement with which the signal is associated.%ENDCOLOR%
   * icon:line_lr %RED%For a signal of a scalar type, the <i>subset of secondary sources</i> is the union of
     all primary sources of all other signals in the same association %BR%
     group (see 11.7).%ENDCOLOR%

%RED%It?s an error if after elaboration the calculation of driving values in a signal association group contains a cyclic dependency on the sources.%ENDCOLOR%

For a signal of a composite type, each composite source is a collection of scalar sources, one for each scalar subelement of the signal. %BR%
It is an error if, after the elaboration of a description, a signal has multiple sources and it is not a resolved signal. It is also an %BR%
error if, after the elaboration of a description, a resolved signal has more sources than the number of elements in the index range of the %BR%
type of the formal parameter of the resolution function associated with the resolved signal.

If a subelement or slice of a resolved signal of composite type is associated as an actual in a port map aspect (either in a component %BR%
instantiation statement, a block statement, or in a binding indication), and if the corresponding formal is of mode out, inout, buffer, or %BR%
linkage, then every scalar subelement of that signal shall be associated exactly once with such a formal in the same port map aspect, and %BR%
the collection of the corresponding formal parts taken together constitute one %RED%primary%ENDCOLOR% source of the signal. If a resolved signal of composite type %BR%
is associated as an actual in a port map aspect, that is equivalent to each of its subelements being associated in the same port map aspect.

If a subelement of a resolved signal of composite type has a driver in a given process, then every scalar subelement of that signal shall %BR%
have a driver in the same process, and the collection of all of those drivers taken together constitute one %RED%primary%ENDCOLOR% source of the signal.

The default value associated with a scalar signal defines the value component of a transaction that is the initial contents of each driver %BR%
(if any) of that signal. The time component of the transaction is not defined, but the transaction is understood to have already occurred %BR%
by the start of simulation.


---+++ (070.1) 11.1 General
<pre>
concurrent_statement ::=
    block_statement
  | process_statement
  | concurrent_procedure_call_statement
  | concurrent_assertion_statement
  | concurrent_signal_assignment_statement
  %RED%| concurrent_signal_association_statement%ENDCOLOR%
  | component_instantiation_statement
  | generate_statement
  | PSL_PSL_Directive
</pre>


---+++ (070.2) 11.7 Concurrent signal association statements %GREEN%[NEW, inserted between 11.6 and 11.7]%ENDCOLOR%
%GREEN%[Editor note: New main paragraph]%ENDCOLOR%

%RED%A concurrent signal association statement represents an association between two signals. Associated signals are said to %BR%
compose an <i>association group</i>. An association group can comprise multiple signals.%ENDCOLOR%
<pre>
%RED%concurrent_signal_association_statement ::=
  [ label <b>:</b> ] concurrent_simple_signal_association

concurrent_simple_signal_association ::=
  <i>lhs</i>_signal_association_target <b><=></b> <i>rhs</i>_signal_association_target ;

signal_association_target ::=
  <i>signal</i>_name%ENDCOLOR%
</pre>

%RED%A signal association implies no direction of information exchange between signal association targets (henceforth referred to as targets). %BR%
If the target in the concurrent signal association statement is a name, then the name shall denote a signal.%ENDCOLOR%

%RED%The signals are associated as follows:%ENDCOLOR%
   * icon:line_lr %RED%If the left-hand side target is a scalar signal and the right-hand side target is also a scalar signal, then both signals are associated.%ENDCOLOR%
   * icon:line_lr %RED%If the left-hand side target is a composite signal and the right-hand side target is also a composite signal, then each subelement in the right-hand %BR%
     side target shall be associated with the corresponding subelement in the left-hand side target.%ENDCOLOR%
   * icon:line_lr %RED%All other cases are an error.%ENDCOLOR%

%RED%All signals in an association group are either resolved or unresolved signals. The targets' subtypes shall be compatible to each other. Moreover, the resolution function %BR%
corresponding to the subtypes shall be the same, if any.%ENDCOLOR%

%RED%If a subelement or slice of a resolved signal of a composite type is associated as the right-hand side target, then every scalar subelement of that %BR%
signal shall be associated exactly once with the corresponding left-hand side target in the same concurrent signal association statement.%ENDCOLOR%

%RED%Note 1 -- A signal association target, denoting a signal name, can also denote an attribute name returning an implicit signal.%ENDCOLOR%

---+++ (070.3) 14.7.3.2 Driving values %GREEN%[Exposed hidden list with a new list hierarchy]%ENDCOLOR%
A basic signal is a signal that has all of the following properties:
   * icon:line_lr It is either a scalar signal or a resolved signal (see 6.4.2.3).
   * icon:line_lr It is not a subelement of a resolved signal.
   * icon:line_lr Is not an implicit signal of the form S'STABLE(T), S'QUIET(T), or S'TRANSACTION (see 16.2).
   * icon:line_lr It is not an implicit signal GUARD (see 11.2).

Basic signals are those that determine the driving values for all other signals.

The driving value of any signal S is determined by the following steps:
   a. If a driving-value release is scheduled for S or for a signal of which S is a subelement, S becomes driving-value released, that is, no %BR%
      longer driving-value forced. Proceed to step b).
   a. If a driving-value force is scheduled for S or for a signal of which S is a subelement, S becomes driving-value forced and the driving value %BR%
      of S is the driving force value for S or the element of the driving force value for the signal of which S is a subelement, as appropriate; no %BR%
      further steps are required. Otherwise, proceed to step c).
   a. If S is driving-value forced, the driving value of S is unchanged from its previous value; no further steps are required. Otherwise, proceed %BR%
      to step d).
   a. If a driving-value deposit is scheduled for S or for a signal of which S is a subelement, the driving value of S is the driving deposit value %BR%
      for S or the element of the driving deposit value for the signal of which S is a subelement, as appropriate; no further steps are required. %BR%
      Otherwise, proceed to step e)%RED%, if S is a basic signal, otherwise proceed to <del>or</del>%ENDCOLOR% f)%RED%<del>, as appropriate</del>%ENDCOLOR%.
   a. If S is a basic signal:
      * icon:line_lr If S has no source, then the driving value of S is given by the default value associated with S (see 6.4.2.3).
      * icon:line_lr If S has one source that is a driver and S is not a resolved signal (see 6.4.2.3), then the driving value of S is the current value of %BR%
        that driver.
      * icon:line_lr If S has one source that is a port and S is not a resolved signal, then the driving value of S is the driving value of the formal part of %BR%
        the association element that associates S with that port (see 6.5.7.1). The driving value of a formal part is obtained by evaluating the %BR%
        formal part as follows: %GRAY%<del>If no conversion function or type conversion is present in the formal part, then the driving value of the formal %BR%
        part is the driving value of the signal denoted by the formal designator. Otherwise, the driving value of the formal part is the value %BR%
        obtained by applying either the conversion function or type conversion (whichever is contained in the formal part) to the driving value of %BR%
        the signal denoted by the formal designator.</del>%ENDCOLOR% %GREEN%[Changed hidden nested item list into a sublist for better readablility]%ENDCOLOR%
         * %GRAY%If no conversion function or type conversion is present in the formal part, then the driving value of the formal part is the driving %BR%
           value of the signal denoted by the formal designator.%ENDCOLOR%
         * %GRAY%Otherwise, the driving value of the formal part is the value obtained by applying either the conversion function or type conversion %BR%
           (whichever is contained in the formal part) to the driving value of the signal denoted by the formal designator.%ENDCOLOR%
      * icon:line_lr If S is a resolved signal and has one or more sources, then the driving values of the sources of S are examined. It is an error if %BR%
        any of these driving values is a composite where one or more subelement values are determined by the null transaction (see 10.5.2.2) and %BR%
        one or more subelement values are not determined by the null transaction. %GRAY%<del>If S is of signal kind register and all the sources of S have %BR%
        values determined by the null transaction, then the driving value of S is unchanged from its previous value. Otherwise, the driving value %BR%
        of S is obtained by executing the resolution function associated with S, where that function is called with an input parameter consisting %BR%
        of the concatenation of the driving values of the sources of S, with the exception of the value of any source of S whose current value is %BR%
        determined by the null transaction.</del>%ENDCOLOR% %GREEN%[Changed hidden nested item list into a sublist for better readablility]%ENDCOLOR%
         * %GRAY%If S is of signal kind register and all the sources of S have values determined by the null transaction, then the driving value of S is %BR%
           unchanged from its previous value.%ENDCOLOR%
         * %GRAY%Otherwise, the driving value of S is obtained by executing the resolution function associated with S, where that function is called %BR%
           with an input parameter consisting of the concatenation of the %RED%current <del>driving</del>%ENDCOLOR% values of the %RED%drivers <del>sources</del>%ENDCOLOR% of S %RED%and the driving  %BR%
           values of the OUT, INOUT, BUFFER, and LINKAGE ports with which S is associated%ENDCOLOR%, with the exception of the value of any source %BR%
           of S whose current value is determined by the null transaction.%ENDCOLOR%
   a.  If S is not a basic signal:
      * icon:line_lr If S is a subelement of a resolved signal R, the driving value of S is the corresponding subelement value of the driving value of R.
      * icon:line_lr Otherwise (S is a nonresolved, composite signal), the driving value of S is equal to the aggregate of the driving values of each of the %BR%
        basic signals that are the subelements of S.

---+++ (070.4) 15.3 Lexical elements, separators, and delimiters

%GREEN%[...]%ENDCOLOR%

A delimiter is either one of the following special characters (in the basic character set):
<pre>
& ' ( ) * + , - . / : ; < = > ` | [ ] ? @
</pre>
or one of the following compound delimiters, each composed of two or more adjacent special characters:
<pre>
=> ** := /= >= <= <> %RED%<=>%ENDCOLOR% ?? ?= ?/= ?< ?<= ?> ?>= << >>
</pre>
%GREEN%[...]%ENDCOLOR%

NOTE 2 -- The following names are used when referring to compound delimiters:

| *Delimiter*        | *Name*                                |
| =>                 | Arrow                                 |
| !**                | Double star, exponentiate             |
| :=                 | Variable assignment                   |
| /=                 | Inequality (pronounced "not equal")   |
| >=                 | Greater than or equal                 |
| <=                 | Less than or equal; signal assignment |
| <>                 | Box                                   |
| %RED%<=>%ENDCOLOR% | %RED%Signal association%ENDCOLOR%     |
| ??                 | Condition conversion                  |
| ?=                 | Matching equality                     |
| ?/=                | Matching inequality                   |
| ?<                 | Matching less than                    |
| ?<=                | Matching less than or equal           |
| ?>                 | Matching greater than                 |
| ?>=                | Matching greater than or equal        |
| <<                 | Double less than                      |
| >>                 | Double greater than                   |

---+++ (070.5) Annex C
%GREEN%[Editor note: Add these rules]%ENDCOLOR%
<pre>
%GREEN%[...]%ENDCOLOR%

concurrent_assertion_statement ::=
  [ label <b>:</b> ] [ <b>postponed</b> ] assertion ;

%RED%concurrent_signal_association_statement ::=
  [ label <b>:</b> ] concurrent_simple_signal_association%ENDCOLOR%

concurrent_conditional_signal_assignment ::=
  target <b><=</b> [ <b>guarded</b> ] [ delay_mechanism ] conditional_waveforms ;

concurrent_procedure_call_statement ::=
  [ label <b>:</b> ] [ <b>postponed</b> ] procedure_call ;

concurrent_selected_signal_assignment ::=
  <b>with</b> expression <b>select</b> [ ? ]
    target <b><=</b> [ <b>guarded</b> ] [ delay_mechanism ] selected_waveforms ;

concurrent_signal_assignment_statement ::=
    [ label <b>:</b> ] [ <b>postponed</b> ] concurrent_simple_signal_assignment
  | [ label <b>:</b> ] [ <b>postponed</b> ] concurrent_conditional_signal_assignment
  | [ label <b>:</b> ] [ <b>postponed</b> ] concurrent_selected_signal_assignment

%RED%concurrent_simple_signal_association ::=
  <i>lhs</i>_signal_association_target <b><=></b> <i>rhs</i>_signal_association_target ;%ENDCOLOR%

concurrent_simple_signal_assignment ::=
  target <b><=</b> [ <b>guarded</b> ] [ delay_mechanism ] waveform ;

concurrent_statement ::=
    block_statement
  | process_statement
  | concurrent_procedure_call_statement
  | concurrent_assertion_statement
  | concurrent_signal_assignment_statement
  %RED%| concurrent_signal_association_statement%ENDCOLOR%
  | component_instantiation_statement
  | generate_statement
  | PSL_PSL_Directive

%GREEN%[...]%ENDCOLOR%

%RED%signal_association_target ::=
  <i>signal</i>_name%ENDCOLOR%
</pre>

---++ Comments

%COMMENT%</sticky>

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Topic revision: r1 - 2017-07-30 - 05:39:59 - TWikiGuest
P1076