/*
This file is part of JOP, the Java Optimized Processor
see <http://www.jopdesign.com/>
Copyright (C) 2001-2008, Martin Schoeberl (martin@jopdesign.com)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package wcet;
import com.jopdesign.sys.*;
public class ShortCrc {
/**
* Set to false for the WCET analysis, true for measurement
*/
final static boolean MEASURE = false;
static int ts, te, to;
/**
* @param args
*/
public static void main(String[] args) {
ts = Native.rdMem(Const.IO_CNT);
te = Native.rdMem(Const.IO_CNT);
to = te-ts;
// measurement + return takes 22+22+21=65 cycles
// WCET measured: 1442/1552
// WCET analysed: 1685-65=1620
// Those numbers are fomr 2006
int min = 0x7fffffff;
int max = 0;
int time = 0;
int val = -1;
for (int i=0; i<100000; ++i) { // @WCA loop=100
val = invoke(val);
time = te-ts-to;
if (time<min) min = time;
if (time>max) max = time;
}
if (MEASURE) System.out.println(min);
if (MEASURE) System.out.println(max);
}
static int invoke(int val) {
int res = measure(val);
if (MEASURE) te = Native.rdMem(Const.IO_CNT);
return res;
}
/*
better values for polynom on short messages see:
'Determining optimal cyclic codes for embedded networks'
(www.cmu.edu)
*/
/**
* claculate crc value with polynom x^8 + x^2 + x + 1
* and initial value 0xff
* on 32 bit data
*/
static int measure(int val) {
if (MEASURE) ts = Native.rdMem(Const.IO_CNT);
int reg = -1;
for (int i=0; i<32; ++i) { // @WCA loop=32
reg <<= 1;
if (val<0) reg |= 1;
val <<=1;
if ((reg & 0x100) != 0) reg ^= 0x07;
}
reg &= 0xff;
return reg;
}
}