IEEE 200X Fast Track Change Proposal

ID:	  FT-19

Proposer:     Jim Lewis 
email:        Jim@SynthWorks.com

Status:       Open
Proposed:     Date
Analyzed:     Date
Resolved:     Date

Enhancement Summary:     process_comb, process_latch, process_ff
Related issues:          
Relevant LRM section:    

Enhancement Detail:
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Processes with implied sensitivity lists and synthesis semantics.


Analysis:
----------------------------
Modifications to 1076-2002

Modify process_statement definition in clause 8.4 to: 
process_statement ::=
  [ process_label : ]
    [ postponed ] process_sensitivity [ is ]
      process_declarative_part
    begin
      process_statement_part
    end [ postponed ] process [ process_label ] ;


Add definition for process_sensitivity in clause 8.4:
process_sensitivity ::=
    process [ ( sensitivity_list ) ]
   | process_comb
   | process_latch
   | process_ff

Add definition for clock_edge in clause 8.4:
clock_edge ::=
  clock_level and event_expr
  | event_expr and clock_level
  clock_level ::= clk_signal_name = '0' | clk_signal_name = '1'
  event_expr ::= clk_signal_name'EVENT | not clk_signal_name'STABLE

Note, the procedures RISING_EDGE and FALLING_EDGE as defined
in IEEE 1164 conform to the above.


Add the following paragraph to clause 8.4:
A process of the form process_comb shall be 
executed as if it contains a sensitivity list 
that has all of the signals read in the process (see 
clause 4.3.2 for a definition of read).  
Software tools (such as lint checkers and synthesis tools) 
can perform additional checks to warn if any behavior within 
a process_comb process does not represent combinational 
logic, such as if rising-edge or level-sensitive storage 
elements are implied.  

A process of the form, process_latch, shall be 
executed as if it contains a sensitivity list 
that has all of the signals read in the process (see 
clause 4.3.2 for a definition of read).  
Software tools can perform additional checks to warn if
any behavior within a process_latch process does
not represent a level sensitive storage element (latch).

A process of the form, process_ff, shall be executed as if
it contains the clock_edge and any signal read independently 
from the clock on the sensitivity list.  Clock_edge shall be 
as defined above.  
Software tools can perform additional checks to warn if
any behavior within a process_latch process does
not represent a latch.


Resolution:
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[To be performed by the 200X Fast Track Working Group]