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dsp: add limits support to SatAddMixin

This commit is contained in:
Robert Jördens 2016-11-19 15:40:42 +01:00
parent 97a54046e8
commit e53d0bcd5b
1 changed files with 26 additions and 14 deletions
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40
artiq/gateware/dsp/tools.py
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@ -29,21 +29,33 @@ def eqh(a, b):
class SatAddMixin: class SatAddMixin:
def sat_add(self, a): """Signed saturating addition mixin"""
def sat_add(self, *a, limits=None, clipped=None):
a = list(a) a = list(a)
# assert all(value_bits_sign(ai)[1] for ai in a) # assert all(value_bits_sign(ai)[1] for ai in a)
n = max(len(ai) for ai in a) length = max(len(ai) for ai in a)
o = log2_int(len(a), need_pow2=False) carry = log2_int(len(a), need_pow2=False)
s = Signal((n + o, True)) full = Signal((length + carry, True))
s0 = Signal((n, True)) limited = Signal((length, True))
z = Signal((1, True)) clip = Signal(2)
if clipped is not None:
clipped.eq(clip)
self.comb += [ self.comb += [
s.eq(reduce(add, a, z)), full.eq(reduce(add, a)),
s0[-1].eq(s[-1]),
If(s[-o-1:] == Replicate(s[-1], o + 1),
s0[:-1].eq(s[:n-1]),
).Else(
s0[:-1].eq(Replicate(~s[-1], n - 1)),
)
] ]
return s0 if limits is None:
self.comb += [
If(full[-1-carry:] == Replicate(full[-1], carry + 1),
limited.eq(full),
clip.eq(0),
).Else(
limited.eq(Cat(Replicate(~full[-1], length - 1), full[-1])),
clip.eq(Cat(full[-1], ~full[-1])),
)
]
else:
self.comb += [
clip.eq(Cat(full < limits[0], full > limits[1])),
limited.eq(Array([full, limits[0], limits[1], 0])[clip]),
]
return limited