synchronous FSM

[Sandhya]

Hi,
I have read that using a single always block(synchronous) for implementing
a state machine is not a good practice.
Can somebody tell me how does the synthesis tool handle this??

Thanks in advance!
Sandhya

 

[rickman]

Sandhya wrote:

Hi,
I have read that using a single always block(synchronous) for implementing
a state machine is not a good practice.
Can somebody tell me how does the synthesis tool handle this??

Did anyone tell you *why* a "single always block" is a bad thing for
FSMs? Most of the time when someone makes a general rule like this,
there is a reason for it that only applies under certain conditions. If
you don't know the conditions, you might as well not use the rule.

I expect you were told this because it is easier to control and optimize
a FSM if the signal on the input to the FFs is a separate entity to
which you can apply attributes. I have done FSMs both ways and it
mainly depends on how complex your FSM is and how fast you need it to
run. If you have a simple machine or it is not pressed for speed, a
single always block is an ok way to code it and is simpler to write and
read.

--

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX