Re: [myhdl-list] Architecture Modelling with MyHDL

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

On Mon, Jul 9, 2012 at 9:45 PM, Uri Nix <ur...@gm...> wrote:
> Hi all,
>
>     I would like to focus a bit on MyHDL's modelling abilities, using a
> simple
>     example to demonstrate an effective development flow.
>
>     Let's consider a circular buffer, implemented as a pure algorithm.
>
> class CBuff(object):
>     def __init__(self, size):
>         self.ram = array.array('B', [0]*size)
>         self.modulo = size
>         self.rd_off = 0
>         self.wr_off = 0
>
>     def write(self, value):
>         self.ram[self.wr_off] = value
>         self.wr_off += 1
>         if self.wr_off >= self.modulo: self.wr_off = 0
>
>     def read(self):
>         value = self.ram[self.rd_off]
>         self.rd_off += 1
>         if self.rd_off >= self.modulo: self.rd_off = 0
>         return value
>
>
>     After fully testing this algorithm, we can add a measure of hardware
>     orientation by making the accesses synchronous (using the same method
>     names, but that of course is a matter of taste):
>
> class HCBuff(CBuff):
>     def write(self, clk, din):
>         @always(clk.posedge)
>         def logic():
>             super(HCBuff, self).write(din.val)
>         return logic
>
>     def read(self, clk, dout):
>         @always(clk.posedge)
>         def logic():
>             dout.next = super(HCBuff, self).read()
>         return logic
>
>
>     We can now perform pretty complicated concurrent simulations with this
>     circular buffer, such as connect each side to a different clock - as
>     demonstrated in the attached test.py.

This is probably quite obvious so please forgive me if this question
is very basic. I don't understand how can you directly call
"super(HCBuff, self).write(din.val)", since in the original write
method self.wr_off is incremented directly, rather than using
self.wr_off.next (which is not possible since self.wr_off is not a
signal). A similar problem occurs with the read method.

What am I missing?

Angel