108 lines
2.7 KiB
C
108 lines
2.7 KiB
C
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/*
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* Copyright (c) 2000 Stephen Williams (steve@icarus.com)
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*
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* This source code is free software; you can redistribute it
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* and/or modify it in source code form under the terms of the GNU
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* General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#if !defined(WINNT) && !defined(macintosh)
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#ident "$Id: vpi_bit.c,v 1.1 2000/03/22 04:26:40 steve Exp $"
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#endif
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# include "vpi_priv.h"
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#define UNAMBIG(v) ((v)&0x0f == (v)>>4)
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# define STREN1(v) ( ((v)&0x80)? ((v)&0xf0) : (0x70 - ((v)&0xf0)) )
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# define STREN0(v) ( ((v)&0x08)? ((v)&0x0f) : (0x07 - ((v)&0x0f)) )
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vpip_bit_t vpip_bits_resolve(const vpip_bit_t*bits, unsigned nbits)
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{
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vpip_bit_t res = bits[0];
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for (idx = 1 ; idx < nbits ; idx += 1) {
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/* High-impedence drives do not affect the result. */
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if (bits[idx] == HiZ)
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continue;
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if (UNAMBIG(res) && UNAMBIG(bits[idx])) {
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/* If both signals are unambiguous, simply choose
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the stronger. */
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if (bits[idx]&0x77 > res&0x77)
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res = bits[idx];
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else if (bits[idx]*0x77 == res&0x77)
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res = (res&0xf0) + (bits[idx]&0x0f);
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else
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;
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} else if (UNAMBIG(res) || UNAMBIG(bits[idx])) {
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/* If one of the signals is unambiguous, then it
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will sweep up the weaker parts of the ambiguous
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signal. The result may be ambiguous, or maybe
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not. */
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vpip_bit_t tmp = 0;
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if (res&0x70 > bits[idx]&0x70)
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tmp |= res&0xf0;
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else
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tmp |= bits[idx]&0xf0;
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if (res&0x07 > bits[idx]&0x07)
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tmp |= res&0x0f;
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else
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tmp |= bits[idx]&0x0f;
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} else {
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/* If both signals are ambiguous, then the result
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has an even wider ambiguity. */
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vpip_bit_t tmp = 0;
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if (STREN1(bits[idx]) > STREN1(res))
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tmp |= bits[idx]&0xf0;
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else
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tmp |= res&0xf0;
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if (STREN0(bits[idx]) < STREN0(res))
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tmp |= bits[idx]&0x0f;
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else
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tmp |= res&0x0f;
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res = tmp;
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}
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}
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if (res&0x77 == 0)
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res = HiZ;
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return res;
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}
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/*
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* $Log: vpi_bit.c,v $
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* Revision 1.1 2000/03/22 04:26:40 steve
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* Replace the vpip_bit_t with a typedef and
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* define values for all the different bit
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* values, including strengths.
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*
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*/
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