diff --git a/litex/soc/cores/code_tmds.py b/litex/soc/cores/code_tmds.py new file mode 100644 index 000000000..70a0994be --- /dev/null +++ b/litex/soc/cores/code_tmds.py @@ -0,0 +1,99 @@ +# +# This file is part of LiteX +# +# Copyright (c) 2015 Sebastien Bourdeauducq +# Copyright (c) 2016-2021 Florent Kermarrec +# SPDX-License-Identifier: BSD-2-Clause + +from functools import reduce +from operator import add + +from migen import * + +# Helpers ------------------------------------------------------------------------------------------ + +control_tokens = [0b1101010100, 0b0010101011, 0b0101010100, 0b1010101011] + +# TMDS Encoder ------------------------------------------------------------------------------------- + +class TMDSEncoder(Module): + def __init__(self): + self.d = Signal(8) + self.c = Signal(2) + self.de = Signal() + + self.out = Signal(10) + + # # # + + # Stage 1 - Count number of 1s in data. + d = Signal(8) + n1d = Signal(max=9) + self.sync += [ + n1d.eq(reduce(add, [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(reduce(add, [~q_m[i] for i in range(8)])), + n1q_m.eq(reduce(add, [q_m[i] for i in range(8)])), + q_m_r.eq(q_m) + ] + + # Stage 4 - Final encoding. + cnt = Signal((6, 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.out[9].eq(~q_m_r[8]), + self.out[8].eq(q_m_r[8]), + If(q_m_r[8], + self.out[:8].eq(q_m_r[:8]), + cnt.eq(cnt + n1q_m - n0q_m) + ).Else( + self.out[:8].eq(~q_m_r[:8]), + cnt.eq(cnt + n0q_m - n1q_m) + ) + ).Else( + If((~cnt[5] & (n1q_m > n0q_m)) | (cnt[5] & (n0q_m > n1q_m)), + self.out[9].eq(1), + self.out[8].eq(q_m_r[8]), + self.out[:8].eq(~q_m_r[:8]), + cnt.eq(cnt + Cat(0, q_m_r[8]) + n0q_m - n1q_m) + ).Else( + self.out[9].eq(0), + self.out[8].eq(q_m_r[8]), + self.out[:8].eq(q_m_r[:8]), + cnt.eq(cnt - Cat(0, ~q_m_r[8]) + n1q_m - n0q_m) + ) + ) + ).Else( + self.out.eq(Array(control_tokens)[s_c]), + cnt.eq(0) + ) + ]