c4m/nmigen/jtag/pmod.py

   1 from nmigen.build import *
   2
   3 __all__ = [
   4     "PmodJTAGResource",
   5 ]
   6
   7
   8 def PmodJTAGResource(*args, pmod_name="pmod", pmod_number, attrs=None,
   9                      master=False, reset=False):
  10     """Get a resource for a JTAG pins on a pmod.
  11
  12     The pins are configured in such a way that the master pmod jtag can
  13     be connected to the tap pmod with a straight cable.
  14
  15     Args:
  16         *args: either number or name, number.
  17         pmod_name (str): name of the pmod connector; default = "pmod"
  18         pmod_number (int): number of pmod connector
  19         attrs (Attrs): attributes for the ``Resource``
  20         master (bool): wether if this a master interface
  21         reset (bool): wether to include a reset signal
  22     """
  23     if master:
  24         mosi = "o"
  25         miso = "i"
  26         tdo_pin = "3"
  27         tdi_pin = "4"
  28     else:
  29         mosi = "i"
  30         miso = "o"
  31         tdo_pin = "4"
  32         tdi_pin = "3"
  33     conn = (pmod_name, pmod_number)
  34
  35     ios = [
  36         Subsignal("tck", Pins("1", dir=mosi, conn=conn)),
  37         Subsignal("tms", Pins("2", dir=mosi, conn=conn)),
  38         Subsignal("tdo", Pins(tdo_pin, dir="o", conn=conn)),
  39         Subsignal("tdi", Pins(tdi_pin, dir="i", conn=conn)),
  40     ]
  41     if reset:
  42         ios.append(Subsignal("trst", PinsN("7", dir=mosi, conn=conn)))
  43     if attrs is not None:
  44         ios.append(attrs)
  45
  46     return Resource.family(*args, default_name="jtag", ios=ios)