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// Chuck Benz, Hollis, NH Copyright (c)2002
//
// The information and description contained herein is the
// property of Chuck Benz.
//
// Permission is granted for any reuse of this information
// and description as long as this copyright notice is
// preserved. Modifications may be made as long as this
// notice is preserved.
// per Widmer and Franaszek
module encode_8b10b (datain, dispin, dataout, dispout) ;
input [8:0] datain ;
input dispin ; // 0 = neg disp; 1 = pos disp
output [9:0] dataout ;
output dispout ;
wire ai = datain[0] ;
wire bi = datain[1] ;
wire ci = datain[2] ;
wire di = datain[3] ;
wire ei = datain[4] ;
wire fi = datain[5] ;
wire gi = datain[6] ;
wire hi = datain[7] ;
wire ki = datain[8] ;
wire aeqb = (ai & bi) | (!ai & !bi) ;
wire ceqd = (ci & di) | (!ci & !di) ;
wire l22 = (ai & bi & !ci & !di) |
(ci & di & !ai & !bi) |
( !aeqb & !ceqd) ;
wire l40 = ai & bi & ci & di ;
wire l04 = !ai & !bi & !ci & !di ;
wire l13 = ( !aeqb & !ci & !di) |
( !ceqd & !ai & !bi) ;
wire l31 = ( !aeqb & ci & di) |
( !ceqd & ai & bi) ;
// The 5B/6B encoding
wire ao = ai ;
wire bo = (bi & !l40) | l04 ;
wire co = l04 | ci | (ei & di & !ci & !bi & !ai) ;
wire do = di & ! (ai & bi & ci) ;
wire eo = (ei | l13) & ! (ei & di & !ci & !bi & !ai) ;
wire io = (l22 & !ei) |
(ei & !di & !ci & !(ai&bi)) | // D16, D17, D18
(ei & l40) |
(ki & ei & di & ci & !bi & !ai) | // K.28
(ei & !di & ci & !bi & !ai) ;
// pds16 indicates cases where d-1 is assumed + to get our encoded value
wire pd1s6 = (ei & di & !ci & !bi & !ai) | (!ei & !l22 & !l31) ;
// nds16 indicates cases where d-1 is assumed - to get our encoded value
wire nd1s6 = ki | (ei & !l22 & !l13) | (!ei & !di & ci & bi & ai) ;
// ndos6 is pds16 cases where d-1 is + yields - disp out - all of them
wire ndos6 = pd1s6 ;
// pdos6 is nds16 cases where d-1 is - yields + disp out - all but one
wire pdos6 = ki | (ei & !l22 & !l13) ;
// some Dx.7 and all Kx.7 cases result in run length of 5 case unless
// an alternate coding is used (referred to as Dx.A7, normal is Dx.P7)
// specifically, D11, D13, D14, D17, D18, D19.
wire alt7 = fi & gi & hi & (ki |
(dispin ? (!ei & di & l31) : (ei & !di & l13))) ;
wire fo = fi & ! alt7 ;
wire go = gi | (!fi & !gi & !hi) ;
wire ho = hi ;
wire jo = (!hi & (gi ^ fi)) | alt7 ;
// nd1s4 is cases where d-1 is assumed - to get our encoded value
wire nd1s4 = fi & gi ;
// pd1s4 is cases where d-1 is assumed + to get our encoded value
wire pd1s4 = (!fi & !gi) | (ki & ((fi & !gi) | (!fi & gi))) ;
// ndos4 is pd1s4 cases where d-1 is + yields - disp out - just some
wire ndos4 = (!fi & !gi) ;
// pdos4 is nd1s4 cases where d-1 is - yields + disp out
wire pdos4 = fi & gi & hi ;
// only legal K codes are K28.0->.7, K23/27/29/30.7
// K28.0->7 is ei=di=ci=1,bi=ai=0
// K23 is 10111
// K27 is 11011
// K29 is 11101
// K30 is 11110 - so K23/27/29/30 are ei & l31
wire illegalk = ki &
(ai | bi | !ci | !di | !ei) & // not K28.0->7
(!fi | !gi | !hi | !ei | !l31) ; // not K23/27/29/30.7
// now determine whether to do the complementing
// complement if prev disp is - and pd1s6 is set, or + and nd1s6 is set
wire compls6 = (pd1s6 & !dispin) | (nd1s6 & dispin) ;
// disparity out of 5b6b is disp in with pdso6 and ndso6
// pds16 indicates cases where d-1 is assumed + to get our encoded value
// ndos6 is cases where d-1 is + yields - disp out
// nds16 indicates cases where d-1 is assumed - to get our encoded value
// pdos6 is cases where d-1 is - yields + disp out
// disp toggles in all ndis16 cases, and all but that 1 nds16 case
wire disp6 = dispin ^ (ndos6 | pdos6) ;
wire compls4 = (pd1s4 & !disp6) | (nd1s4 & disp6) ;
assign dispout = disp6 ^ (ndos4 | pdos4) ;
assign dataout = {(jo ^ compls4), (ho ^ compls4),
(go ^ compls4), (fo ^ compls4),
(io ^ compls6), (eo ^ compls6),
(do ^ compls6), (co ^ compls6),
(bo ^ compls6), (ao ^ compls6)} ;
endmodule
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