please help me!!
i have written a program to calculate 32 bit CRC(used for ETHERNET)..but its not working and giving correct output..
please let me know my mistakes..
output should be :E7 B0 51 93 - /************** program starts here *************************/
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typedef unsigned long ul;
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typedef unsigned char uchar;
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uchar buffer_bytes[64] = {0x00,0x14,0x85,0x31,0x24,0x10,0x00,0x15,0x00,0x15,0x9f,0x07,0x08,0x06,0x00,0x01,0x08,0x00,0x06,0x04,0x00,0x02,0x00,0x15,0x00,0x15,0x9f,0x07,0xc0,0xa8,0x00,0x02,0x00,0x14,0x85,0x31,0x24,0x10,0xc0,0xa8,0x00,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
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ul remainder ,temp; //to get 32 bit number
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unsigned short weld,joint;
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unsigned char i,count = 0 ,str_length =64, *ptr,j;
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#define MSB 0x80000000;
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#define POLY 0x04C11DB7
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#define printf printf_fast_f
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void init_uart(void)
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{
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ES = 0 ; //Disable serial interrupt.
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SCON = 0x50 ; //mode 0,REN enabled
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BDRCON = 0x0E ; //
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PCON &= 0x7F ;
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BRL = 224 ;
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BDRCON |= 0x10 ;
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}
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void putchar(uchar send_this)
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{
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uart_send_char(send_this);
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}
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void main(void)
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{
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init_uart();
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ptr = &buffer_bytes[0];
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//----------------------------------------------------------------------------------------------------------/
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// get 32 bit number out of the whole string /
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//----------------------------------------------------------------------------------------------------------/
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weld = (unsigned short)*ptr;
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ptr++;
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weld = ((weld << 8) & 0xff00) + (unsigned short)*ptr; //16 bit number higher
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ptr++;
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joint = (unsigned short)*ptr;
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ptr ++;
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joint = ((joint << 8) &0xff00) + (unsigned short) *ptr ; //16 bit number lower
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ptr ++; //pointer points the next byte after 4th byte
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remainder = weld;
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remainder = (remainder << 16) & 0xffff0000 ;
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remainder = remainder + joint; //32 bit number
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//remainder = remainder ^ (ul) 0xFFFFFFFF;
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//----------------------------------------------------------------------------------------------------
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//str_length = str_length - 4;
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for(j = str_length; j>0 ; j--) //str_length = no. of bytes in string
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{
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if((remainder & (ul)0xFF000000)==0x00000000)
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{
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remainder = remainder << 8;
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remainder = (remainder & (ul)0xFFFFFF00) | (ul)*ptr;
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}
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else
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{
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for(i=0; i<8 ; i++)
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{
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printf(" %lx\r\n",remainder);
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if((remainder & (ul)0x80000000) == (ul)0x80000000) //if MSB is high then shift left by 1, get next bit 0
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{
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remainder = remainder << 1;
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if((*ptr & 0x80) == 0x80)
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{
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remainder |= (ul)0x00000001;
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}
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else
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{
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remainder |= (ul)0x00000000;
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}
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*ptr = *ptr << 1; //XOR remainder with POLY
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printf("msg %lx\r\n",remainder);
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remainder = remainder ^ (ul)0x04C11DB7;
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printf("XOR abov msg wiD POLY\r\n");
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}
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else
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{
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// while((remainder & (ul)0x80000000) == (ul)0x00000000)
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// {
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remainder = remainder << 1;
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if((*ptr & 0x80) == 0x80)
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{
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remainder |= (ul)0x00000001;
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}
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else
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{
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remainder |= (ul)0x00000000;
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}
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*ptr = *ptr << 1;
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// i++;
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// if (i >= 8)break;
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//}
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}
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}
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ptr ++;
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//printf("ptr = %2x\r\n",*ptr);
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}
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}
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