Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

synthesis tool evaluation of multiple always blocks.

Status
Not open for further replies.

ASIC_int

Advanced Member level 4
Joined
May 14, 2011
Messages
118
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Activity points
2,234
Does synthesis tool evaluate the always blocks one after another instead of concurrently if there are more than one always block in one module?
 

lostinxlation

Advanced Member level 3
Joined
Aug 19, 2010
Messages
701
Helped
197
Reputation
394
Reaction score
184
Trophy points
1,323
Location
San Jose area
Activity points
5,051
What difference do synthesis tools make by "evaluating" always' sequentially or concurrently ? A synthesis is not a simulation.
 

ASIC_int

Advanced Member level 4
Joined
May 14, 2011
Messages
118
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Activity points
2,234
But an RTL goes for simulation as well as synthesis. Synthesis output may depend on sequential and concurrent evaluation of always blocks.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
48,174
Helped
14,198
Reputation
28,655
Reaction score
12,887
Trophy points
1,393
Location
Bochum, Germany
Activity points
279,122
In fact, the order of evaluation matters for a few cases, where blocking assignments are made in one always block and the result is used in the other. Although synthesized hardware doesn't work sequentially (or has a hardware equivalent of a blocking assignments), the evaluation oder of the behavioral description affects the synthesis result. The simple rule is to avoid all constructs that have unpredictable results related to unknown evaluation order.

But the problem is clearly stated in the Verilog specification and many text books, I don't see any source of doubt in this regard.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top