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framebuffer/dvi: add TMDS encoder (untested)
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Sebastien Bourdeauducq
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Sep 16, 2013
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from migen.fhdl.std import * | ||
from migen.genlib.misc import optree | ||
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control_tokens = [0b1101010100, 0b0010101011, 0b0101010100, 0b1010101011] | ||
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class Encoder(Module): | ||
def __init__(self): | ||
self.d = Signal(8) | ||
self.c = Signal(2) | ||
self.de = Signal() | ||
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self.output = Signal(10) | ||
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### | ||
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# stage 1 - count number of 1s in data | ||
d = Signal(8) | ||
n1d = Signal(max=9) | ||
self.sync += [ | ||
n1d.eq(optree("+", [self.d[i] for i in range(8)])), | ||
d.eq(self.d) | ||
] | ||
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# stage 2 - add 9th bit | ||
q_m = Signal(9) | ||
q_m8_n = Signal() | ||
self.comb += q_m8_n.eq((n1d > 4) | ((n1d == 4) & ~d[0])) | ||
for i in range(8): | ||
if i: | ||
curval = curval ^ d[i] ^ q_m8_n | ||
else: | ||
curval = d[0] | ||
self.sync += q_m[i].eq(curval) | ||
self.sync += q_m[8].eq(~q_m8_n) | ||
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# stage 3 - count number of 1s and 0s in q_m[:8] | ||
q_m_r = Signal(9) | ||
n0q_m = Signal(max=9) | ||
n1q_m = Signal(max=9) | ||
self.sync += [ | ||
n0q_m.eq(optree("+", [~q_m[i] for i in range(8)])), | ||
n1q_m.eq(optree("+", [q_m[i] for i in range(8)])), | ||
q_m_r.eq(q_m) | ||
] | ||
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# stage 4 - final encoding | ||
cnt = Signal((5, True)) | ||
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s_c = self.c | ||
s_de = self.de | ||
for p in range(3): | ||
new_c = Signal(2) | ||
new_de = Signal() | ||
self.sync += new_c.eq(s_c), new_de.eq(s_de) | ||
s_c, s_de = new_c, new_de | ||
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self.sync += If(s_de, | ||
If((cnt == 0) | (n1q_m == n0q_m), | ||
self.output[9].eq(~q_m_r[8]), | ||
self.output[8].eq(q_m_r[8]), | ||
If(q_m_r[8], | ||
self.output[:8].eq(q_m_r[:8]), | ||
cnt.eq(cnt + n1q_m - n0q_m) | ||
).Else( | ||
self.output[:8].eq(~q_m_r[:8]), | ||
cnt.eq(cnt + n0q_m - n1q_m) | ||
) | ||
).Else( | ||
If((~cnt[4] & (n1q_m > n0q_m)) | (cnt[4] & (n0q_m > n1q_m)), | ||
self.output[9].eq(1), | ||
self.output[8].eq(q_m_r[8]), | ||
self.output[:8].eq(~q_m_r[:8]), | ||
cnt.eq(cnt + Cat(0, q_m_r[8]) + n0q_m - n1q_m) | ||
).Else( | ||
self.output[9].eq(0), | ||
self.output[8].eq(q_m_r[8]), | ||
self.output[:8].eq(q_m_r[:8]), | ||
cnt.eq(cnt - Cat(0, ~q_m_r[8]) + n1q_m - n0q_m) | ||
) | ||
) | ||
).Else( | ||
self.output.eq(Array(control_tokens)[s_c]), | ||
cnt.eq(0) | ||
) | ||
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if __name__ == "__main__": | ||
from migen.fhdl import verilog | ||
print(verilog.convert(Encoder())) |