📄 distances.py
字号:
########################################################################## ######## distances.py ######## ######## This file is part of the turbo decoder IP core project ######## http://www.opencores.org/projects/turbocodes/ ######## ######## Author(s): ######## - David Brochart(dbrochart@opencores.org) ######## ######## All additional information is available in the README.txt ######## file. ######## ############################################################################## ######## Copyright (C) 2005 Authors ######## ######## This source file may be used and distributed without ######## restriction provided that this copyright statement is not ######## removed from the file and that any derivative work contains ######## the original copyright notice and the associated disclaimer. ######## ######## This source file is free software; you can redistribute it ######## and/or modify it under the terms of the GNU Lesser General ######## Public License as published by the Free Software Foundation; ######## either version 2.1 of the License, or (at your option) any ######## later version. ######## ######## This source is distributed in the hope that it will be ######## useful, but WITHOUT ANY WARRANTY; without even the implied ######## warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ######## PURPOSE. See the GNU Lesser General Public License for more ######## details. ######## ######## You should have received a copy of the GNU Lesser General ######## Public License along with this source; if not, download it ######## from http://www.opencores.org/lgpl.shtml ######## ##########################################################################from misc import opposite, adder, registerfrom myhdl import Signal, intbv, always_comb, instancesdef partDistance(a, b, y1, y2, res, ref = intbv(0, 0, 8)): """ Partial distance from (a, b, y1, y2) = ref. ref -- reference to compute the distance from a, b, y1, y2 -- in : decoder input signals, coded with n bits res -- out : partial distance signal, coded with (n + 2) bits """ while 1:# def partDistanceLogic(): if ref[2] == 0: bSigned = b.val else: bSigned = -b.val if ref[1] == 0: y1Signed = y1.val else: y1Signed = -y1.val if ref[0] == 0: y2Signed = y2.val else: y2Signed = -y2.val res.next = a.val + bSigned + y1Signed + y2Signed yield a, b, y1, y2# return always_comb(partDistanceLogic)def distance(partDist, z, dist, n = 4): """ Distance computation. n -- number of bits for the coding of the decoder input signals partDist -- in : sum of the decoder input signals z -- in : extrinsic information dist -- out : distance """ def distanceLogic(): dist.next = (4 * (2 ** (n - 1) - 1) + partDist.val) / 2 + z.val return always_comb(distanceLogic)def distances(a, b, y1, y2, z, distance16, n = 4): """ Computes the 16 distances from the decoder input signals. n -- number of bits for the coding of the decoder input signals a, b, y1, y2 -- in : decoder input signals, coded with n bits z -- in : extrinsic information signals (x4), coded with m bits distance16 -- out : distance signals (x16) """ partDist = [Signal(intbv(0, -(2**(n+1)), 2**(n+1))) for i in range(16)] opposite_i = [None for i in range(8)] distance_i = [None for i in range(16)] partDistance_i = [None for i in range(8)] for i in range(8): partDistance_i[i] = partDistance(a, b, y1, y2, partDist[i], intbv(i, 0, 8)) for i in range(8): opposite_i[i] = opposite(partDist[i], partDist[15 - i]) for i in range(16): distance_i[i] = distance(partDist[i], z[i / 4], distance16[i], n) return instances()def reduction(org, chd, q = 8): """ (Reduction: if anyone's q(th) bit is set, divide everyone by 2.) Temporary test: when everyone's q(th) bit is set, reset everyone's q(th) bit. q -- accumulated distance width org -- in : original array of 8 q-bit accumulated distances chd -- out : reduced array of 8 q-bit accumulated distances """# tmp = intbv(0, 0, 2**q) while 1:# msb = bool(0) msb = bool(1) for i in range(8):# msb = msb or org[i].val[q-1] msb = msb and org[i].val[q - 1] for i in range(8): chd[i].next[q-1:0] = org[i].val[q-1:0] chd[i].next[q - 1] = (not msb) and org[i].val[q - 1]# if msb == 1:# tmp[q-1:0] = org[i].val[q:1]# else:# tmp = org[i].val# chd[i].next = tmp yield org[0], org[1], org[2], org[3], org[4], org[5], org[6], org[7]def accDist(clk, rst, accDistReg, dist, accDistNew, q = 8): """ Accumulated distances. q -- in : accumulated distance width clk, rst -- in : clock and negative reset accDistReg -- in : original array of 8 q-bit accumulated distance registers dist -- in : array of 16 distances accDistNew -- out : array of 32 (q+1)-bit accumulated distances """ adder_i = [None for i in range(32)] register_i = [None for i in range(8)] accDistOld = [Signal(intbv(0, 0, 2**q)) for i in range(8)] accDistRed = [Signal(intbv(0, 0, 2**q)) for i in range(8)] accDistRegSorted = [Signal(intbv(0, 0, 2**q)) for i in range(8)] accDistRegDelta = [Signal(intbv(0, 0, 2**q)) for i in range(8)] distIndex = [0, 7, 11, 12, 0, 7, 11, 12, 2, 5, 9, 14, 2, 5, 9, 14, 3, 4, 8, 15, 3, 4, 8, 15, 1, 6, 10, 13, 1, 6, 10, 13] for i in range(32): adder_i[i] = adder(accDistOld[i/4], dist[distIndex[i]], accDistNew[i]) reduction_i0 = reduction(accDistReg, accDistRed, q) for i in range(8): register_i[i] = register(clk, rst, accDistRed[i], accDistOld[i]) return instances()⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -