litex/milkymist/framebuffer/dvi.py

89 lines
2.1 KiB
Python

from migen.fhdl.std import *
from migen.genlib.misc import optree
control_tokens = [0b1101010100, 0b0010101011, 0b0101010100, 0b1010101011]
class Encoder(Module):
def __init__(self):
self.d = Signal(8)
self.c = Signal(2)
self.de = Signal()
self.output = Signal(10)
###
# 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)
]
# 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)
# 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)
]
# stage 4 - final encoding
cnt = Signal((5, True))
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
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)
)
if __name__ == "__main__":
from migen.fhdl import verilog
print(verilog.convert(Encoder()))