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fastlink: rework crc injection

This commit is contained in:
Robert Jördens 2020-08-23 19:41:13 +00:00
parent a27a03ab3c
commit 63e4b95325
1 changed files with 13 additions and 13 deletions
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26
artiq/gateware/rtio/phy/fastlink.py
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@ -23,7 +23,7 @@ class SerDes(Module):
* `n_crc` CRC bits per frame for divisor poly `poly`
"""
# pins
self.data = [Signal(2) for _ in range(n_data)]
self.data = [Signal(2, reset_less=True) for _ in range(n_data)]
n_mosi = n_data - 2 # mosi lanes
n_word = n_mosi*t_clk # bits per word
t_frame = t_clk*n_frame # frame duration
@ -48,6 +48,7 @@ class SerDes(Module):
# build from LSB to MSB because MSB first
for i in range(n_frame): # iterate over words
if i == 0: # data and checksum
words_.append(C(0, n_crc))
k = n_word - n_crc
elif i == 1: # marker
words_.append(C(1))
@ -61,30 +62,31 @@ class SerDes(Module):
words_.append(self.payload[j:j + k])
j += k
words_ = Cat(words_)
assert len(words_) == n_frame*n_word - n_crc
assert len(words_) == n_frame*n_word
words = Signal(len(words_))
self.comb += words.eq(words_)
clk = Signal(t_clk, reset=d_clk)
i = Signal(max=t_frame//2)
# big shift register for clk and mosi
sr = [Signal(t_frame - n_crc//n_mosi, reset_less=True)
for i in range(n_mosi)]
# big shift register for mosi and
sr = [Signal(t_frame, reset_less=True) for i in range(n_mosi)]
assert len(Cat(sr)) == len(words)
# DDR bits for each register
crc_data = [sri[-2] for sri in sr] + [sri[-1] for sri in sr]
sr_t = [sr[i % n_mosi][i//n_mosi] for i in range(len(words))]
data_t = ([d[0] for d in self.data[:-1]] +
[d[1] for d in self.data[:-1]])
miso_sr = Signal(t_frame, reset_less=True)
miso_sr_next = Signal.like(miso_sr)
self.comb += [
self.stb.eq(i == t_frame//2 - 1),
# LiteETHMACCRCEngine takes data LSB first
self.crc.data.eq(Cat(reversed(crc_data))),
self.crc.data.eq(Cat(reversed(sr_t[-2*n_mosi:]))),
miso_sr_next.eq(Cat(self.data[-1], miso_sr)),
[di.eq(sri[-2:]) for di, sri in zip(self.data, [clk] + sr)],
]
self.sync.rio_phy += [
# shift everything by two bits
[sri.eq(Cat(sri[-2:], sri)) for sri in [clk] + sr],
[di.eq(sri[-2:]) for di, sri in zip(self.data, [clk] + sr)],
clk.eq(Cat(clk[-2:], clk)),
[sri.eq(Cat(C(0, 2), sri)) for sri in sr],
miso_sr.eq(miso_sr_next),
self.crc.last.eq(self.crc.next),
i.eq(i + 1),
@ -97,10 +99,8 @@ class SerDes(Module):
# unload miso
self.readback.eq(Cat([miso_sr_next[t_miso + i*t_clk]
for i in range(n_frame)])),
),
If(i == t_frame//2 - 2,
# inject crc for the last cycle
Cat(crc_data[-n_crc:]).eq(self.crc.next),
Cat(data_t[-n_crc:]).eq(self.crc.next),
),
]