Re: [myhdl-list] intb min, max confusion

[Angel E. <ang...@gm...>]

I think the comparison to range is not totally accurate. The docstring
of the range function is as follows:

    range([start,] stop[, step]) -> list of integers

That is, there is no "max" parameter, but a "stop" parameter.
I'm not saying the current behavior should be changed, just that
perhaps the parameter name is a bit misleading.

Cheers,

Angel


On Thu, Oct 4, 2012 at 4:48 AM, Christopher Felton
<chr...@gm...> wrote:
> You would simply use MAXV = 2**NBITS.  This is common in
> Python (there is a term for it).  Example if you use "range(3)"
> the list you get is 0,1,2.  It doesn't include the 3 only up to.
> The intbv works the same, max=N, the max value will be
> N-1.  Even though a 3bit value was created "len(x) == 3" the max
> value was specified and is checked during simulation.
>
> Hope that helps,
> Chris
>
>
> On Wed, Oct 3, 2012 at 6:53 PM, garyr <ga...@fi...> wrote:
>>
>> It appears to me that the max limit on an intbv value should be > (greater
>> than) rather than >= (greater than or equal). In the following code, isn't
>> 3
>> a valid value for a 3-bit signal?
>>
>> from myhdl import *
>> def testBench():
>>     @instance
>>     def stimulus():
>>         NBITS = 3
>>         MAXV = 2**(NBITS-1)
>>         min = -MAXV
>>         max = MAXV-1
>>         print 'NBITS=%d   min=%d   max=%d' % (NBITS, min, max)
>>         x = Signal(intbv(0, min=min, max=max))
>>         x.next = min
>>         yield delay(1)
>>         print 'x', x
>>         x.next = max
>>         yield delay(1)
>>         print 'x', x
>>         raise StopSimulation
>>     return instances()
>> tb = testBench()
>> Simulation(tb).run(200)
>> ======================================
>> >python intbTest.py
>> NBITS=3   min=-4   max=3
>> x -4
>> Traceback (most recent call last):
>>   File "intbTest.py", line 22, in <module>
>>     Simulation(tb).run(200)
>>   File "C:\Python26\lib\site-packages\myhdl\_Simulation.py", line 132, in
>> run
>>     waiter.next(waiters, actives, exc)
>>   File "C:\Python26\lib\site-packages\myhdl\_Waiter.py", line 128, in next
>>     clause = self.generator.next()
>>   File "intbTest.py", line 15, in stimulus
>>     x.next = max
>>   File "C:\Python26\lib\site-packages\myhdl\_Signal.py", line 200, in
>> _set_next
>>     self._setNextVal(val)
>>   File "C:\Python26\lib\site-packages\myhdl\_Signal.py", line 266, in
>> _setNextIntbv
>>     self._next._checkBounds()
>>   File "C:\Python26\lib\site-packages\myhdl\_intbv.py", line 79, in
>> _checkBounds
>>     (self._val, self._max))
>> ValueError: intbv value 3 >= maximum 3
>> >Exit code: 1
>>
>>
>>
>>
>>
>>
>>
>>
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>
>
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