Re: [myhdl-list] TypeError: Unexpected type

[Christopher F. <chr...@gm...>]

On 3/24/2015 9:30 AM, Guy Eschemann wrote:
> from myhdl import *
>
> def mpegChannel(clk, rst):
>
>      s_tx_data_xor_mask_r = Signal(intbv(0)[1 + 31:])
>
>      @always_seq(clk.posedge, rst)
>      def fsm_seq():
>          for i in range(4):
>              if i == 0:
>                  s_tx_data_xor_mask_r.next[1 + 7:0] = 0
>              elif i == 1:
>                  s_tx_data_xor_mask_r.next[1 + 15:8] = 1
>              elif i == 2:
>                  s_tx_data_xor_mask_r.next[1 + 23:16] = 2
>              else:
>                  s_tx_data_xor_mask_r.next[1 + 31:24] = 3
>
>      return instances()


I think this is a bug / limitation and an issue should
to be created (but there might be a good reason for the
limitation that I can't think of right now).

You can work around it with:

In [5]: from myhdl import *
    ...:
    ...: def mpegChannel(clk, rst):
    ...:
    ...:     s_tx_data_xor_mask_r = Signal(intbv(0)[1 + 31:])

    ...:     # *** limited range type for switch ***
    ...:     full_case = intbv(0, min=0, max=4)

    ...:     @always_seq(clk.posedge, rst)
    ...:     def fsm_seq():
    ...:         for i in range(4):
    ...:             full_case[:] = i
    ...:             if full_case == 0:
    ...:                 s_tx_data_xor_mask_r.next[1 + 7:0] = 0
    ...:             elif full_case == 1:
    ...:                 s_tx_data_xor_mask_r.next[1 + 15:8] = 1
    ...:             elif full_case == 2:
    ...:                 s_tx_data_xor_mask_r.next[1 + 23:16] = 2
    ...:             else:
    ...:                 s_tx_data_xor_mask_r.next[1 + 31:24] = 3
    ...:
    ...:     return instances()

The limitation is, when evaluating an if-else structure
the conversion code wants to determine if it full-case
or not, because the variable switched on is an `int` it
throws the type error.  But the code example seems reasonable,
I think?

Regards,
Chris