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lib.io: allow Pin(xdr=0), representing a combinatorial I/O buffer.

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This commit is contained in:
whitequark 2019-06-03 03:29:27 +00:00
parent 3327deae92
commit c30617fc05
2 changed files with 49 additions and 9 deletions
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17
nmigen/lib/io.py
View file

@ -18,19 +18,19 @@ def pin_layout(width, dir, xdr=1):
if dir not in ("i", "o", "io"):
raise TypeError("Direction must be one of \"i\", \"o\" or \"io\", not '{!r}'"""
.format(dir))
if not isinstance(xdr, int) or xdr < 1:
raise TypeError("Gearing ratio must be a positive integer, not '{!r}'"
if not isinstance(xdr, int) or xdr < 0:
raise TypeError("Gearing ratio must be a non-negative integer, not '{!r}'"
.format(xdr))
fields = []
if dir in ("i", "io"):
if xdr == 1:
if xdr in (0, 1):
fields.append(("i", width))
else:
for n in range(xdr):
fields.append(("i{}".format(n), width))
if dir in ("o", "io"):
if xdr == 1:
if xdr in (0, 1):
fields.append(("o", width))
else:
for n in range(xdr):
@ -60,7 +60,8 @@ class Pin(Record):
is specified, both the ``i``/``iN`` and ``o``/``oN`` signals are present, and an ``oe``
signal is present.
xdr : int
Gearbox ratio. If equal to 1, the I/O buffer is SDR, and only ``i``/``o`` signals are
Gearbox ratio. If equal to 0, the I/O buffer is combinatorial, and only ``i``/``o``
signals are present. If equal to 1, the I/O buffer is SDR, and only ``i``/``o`` signals are
present. If greater than 1, the I/O buffer includes a gearbox, and ``iN``/``oN`` signals
are present instead, where ``N in range(0, N)``. For example, if ``xdr=2``, the I/O buffer
is DDR; the signal ``i0`` reflects the value at the rising edge, and the signal ``i1``
@ -72,13 +73,13 @@ class Pin(Record):
----------
i : Signal, out
I/O buffer input, without gearing. Present if ``dir="i"`` or ``dir="io"``, and ``xdr`` is
equal to 1.
equal to 0 or 1.
i0, i1, ... : Signal, out
I/O buffer inputs, with gearing. Present if ``dir="i"`` or ``dir="io"``, and ``xdr`` is
greater than 1.
o : Signal, in
I/O buffer output, without gearing. Present if ``dir="o"`` or ``dir="io"``, and ``xdr`` is
equal to 1.
equal to 0 or 1.
o0, o1, ... : Signal, in
I/O buffer outputs, with gearing. Present if ``dir="o"`` or ``dir="io"``, and ``xdr`` is
greater than 1.
@ -86,7 +87,7 @@ class Pin(Record):
I/O buffer output enable. Present if ``dir="io"``. Buffers generally cannot change
direction more than once per cycle, so at most one output enable signal is present.
"""
def __init__(self, width, dir, xdr=1, name=None):
def __init__(self, width, dir, xdr=0, name=None):
self.width = width
self.dir = dir
self.xdr = xdr

41
nmigen/test/test_lib_io.py
View file

@ -4,7 +4,7 @@ from ..hdl.rec import *
from ..lib.io import *
class PinLayoutSDRTestCase(FHDLTestCase):
class PinLayoutCombTestCase(FHDLTestCase):
def test_pin_layout_i(self):
layout_1 = pin_layout(1, dir="i")
self.assertEqual(layout_1.fields, {
@ -43,6 +43,45 @@ class PinLayoutSDRTestCase(FHDLTestCase):
})
class PinLayoutSDRTestCase(FHDLTestCase):
def test_pin_layout_i(self):
layout_1 = pin_layout(1, dir="i", xdr=1)
self.assertEqual(layout_1.fields, {
"i": ((1, False), DIR_NONE),
})
layout_2 = pin_layout(2, dir="i", xdr=1)
self.assertEqual(layout_2.fields, {
"i": ((2, False), DIR_NONE),
})
def test_pin_layout_o(self):
layout_1 = pin_layout(1, dir="o", xdr=1)
self.assertEqual(layout_1.fields, {
"o": ((1, False), DIR_NONE),
})
layout_2 = pin_layout(2, dir="o", xdr=1)
self.assertEqual(layout_2.fields, {
"o": ((2, False), DIR_NONE),
})
def test_pin_layout_io(self):
layout_1 = pin_layout(1, dir="io", xdr=1)
self.assertEqual(layout_1.fields, {
"i": ((1, False), DIR_NONE),
"o": ((1, False), DIR_NONE),
"oe": ((1, False), DIR_NONE),
})
layout_2 = pin_layout(2, dir="io", xdr=1)
self.assertEqual(layout_2.fields, {
"i": ((2, False), DIR_NONE),
"o": ((2, False), DIR_NONE),
"oe": ((1, False), DIR_NONE),
})
class PinLayoutDDRTestCase(FHDLTestCase):
def test_pin_layout_i(self):
layout_1 = pin_layout(1, dir="i", xdr=2)