124 lines
4.0 KiB
Python
124 lines
4.0 KiB
Python
from migen import *
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from misoc.cores.code_8b10b import SingleEncoder, Decoder
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class MultiEncoder(Module):
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# For 4-channel EEM
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# Thus, no need for words parameter
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# It is always a 2-wds -> 4-ch conversion
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# Implement using crossbar, so we don't need to do clock domain conversion
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# while maintaining proper disparity
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def __init__(self, lsb_first=False):
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WORDS = 2
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# Keep the link layer interface identical to standard encoders
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self.d = [Signal(8) for _ in range(WORDS)]
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self.k = [Signal() for _ in range(WORDS)]
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# Output interface is simplified because we have custom physical layer
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self.output = [Signal(10) for _ in range(WORDS)]
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# Module start signal
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self.start = Signal()
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# lsb_first should not be set set
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# But technically if the same setting is reflected on the decoder
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# It shouldn't be an issue
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if lsb_first:
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raise ValueError("lsb_first must not be set")
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# Phase of the encoder
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# Alternate crossbar between encoder and SERDES every cycle
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phase = Signal()
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# Intermediate registers for output and disparity
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# More significant bits are buffered due to channel geometry
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# Disparity bit is delayed. The same encoder is shared by 2 SERDES
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output_bufs = [Signal(5) for _ in range(WORDS)]
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disp_bufs = [Signal() for _ in range(WORDS)]
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encoders = [SingleEncoder(lsb_first) for _ in range(WORDS)]
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self.submodules += encoders
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for d, k, output, output_buf, disp_buf, encoder in \
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zip(self.d, self.k, self.output, output_bufs, disp_bufs, encoders):
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self.comb += [
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encoder.d.eq(d),
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encoder.k.eq(k),
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encoder.disp_in.eq(disp_buf),
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# Implementing switching crossbar
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If(phase,
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output.eq(Cat(encoder.output[0:5], output_buf))
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).Else(
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output.eq(Cat(output_buf, encoder.output[0:5]))
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),
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]
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# Handle intermediate registers
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self.sync += [
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disp_buf.eq(encoder.disp_out),
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output_buf.eq(encoder.output[5:10]),
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]
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aligned = Signal()
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self.sync += [
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# Phase switching
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phase.eq(~phase),
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If(~aligned & self.start,
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aligned.eq(1),
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# Later statements take precedent
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phase.eq(0),
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),
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]
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# Unlike the usual 8b10b decoder, it needs to know which SERDES to decode
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class CrossbarDecoder(Module):
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def __init__(self, lsb_first=False):
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self.raw_input = Signal(10)
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self.d = Signal(8)
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self.k = Signal()
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# Notifier signal when group alignmnet is completed
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self.start = Signal()
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aligned = Signal()
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phase = Signal()
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# Intermediate register for input
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buffer = Signal(5)
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self.submodules.decoder = Decoder(lsb_first)
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# lsb_first should not be set set
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# But technically if the same setting is reflected on the decoder
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# It shouldn't be an issue
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if lsb_first:
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raise ValueError("lsb_first must not be set")
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# Update phase & synchronous elements
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self.sync += [
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phase.eq(~phase),
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If(~aligned & self.start,
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aligned.eq(1),
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phase.eq(0),
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),
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If(phase,
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buffer.eq(self.raw_input[:5]),
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).Else(
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buffer.eq(self.raw_input[5:])
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),
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]
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# Send appropriate input to decoder
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self.comb += [
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If(phase,
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self.decoder.input.eq(Cat(buffer, self.raw_input[5:])),
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).Else(
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self.decoder.input.eq(Cat(buffer, self.raw_input[:5])),
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),
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]
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self.comb += [
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self.d.eq(self.decoder.d),
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self.k.eq(self.decoder.k),
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]
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