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albe01
Joined: 02 Jul 2010
Posts: 30
Location: italy
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| Help! I want a function equivalent to that in ccs... |
 Posted: Fri Jul 16, 2010 7:20 am |
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hello to everyone, I want a function equivalent to that
I did many tests, but have not found anything equivalent working
i use a pic 18F4525 and this function work only on the 16F
| Code: |
#asm //embedded assembly language route to do a 16 bit rotate
BCF 03,0
RRF fcshi,F
RRF fcslo,F
#endasm
suggestions are welcome
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Ttelmah
Joined: 11 Mar 2010
Posts: 19497
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| Posted: Fri Jul 16, 2010 8:43 am |
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The function you have there, performs a _shift_, not a rotation. If you look, the bit off the bottom is lost, and a zero is shifted in from the carry (which is why it is cleared in the first instruction).
Look at the code generated by the CCS 'shift_right' function:
| Code: |
.................... shift_right(&val,2,0);
00C3: BCF 03.0
00C4: RRF 47,F
00C5: RRF 46,F
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identical (except I'm using 'val', rather than 'fcs'.
The CCS instruction happily works on the PIC18, knowing that the carry flag is now in the register at address 0xFD8, rather than '3' on the PIC16, and that the PIC18 has separate rotate instructions to handle the carry, so has to use RRCF, rather than RRF.
Use the CCS instruction, it'll help make the code portable to different processors....
Best Wishes |
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KnowMore
Joined: 05 Jul 2010
Posts: 9
Location: Vietnam
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| Posted: Fri Jul 16, 2010 10:28 am |
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| Code: | rotate_right( )
--------------------------------------------------------------------------------
Syntax:
rotate_right (address, bytes)
Parameters:
address is a pointer to memory, bytes is a count of the number of bytes to work with.
Returns:
undefined
Function:
Rotates a bit through an array or structure. The address may be an array identifier or an address to a byte or structure (such as &data). Bit 0 of the lowest BYTE in RAM is considered the LSB.
Availability:
All devices
Requires:
Nothing
Examples:
struct {
int cell_1 : 4;
int cell_2 : 4;
int cell_3 : 4;
int cell_4 : 4; } cells;
rotate_right( &cells, 2);
rotate_right( &cells, 2);
rotate_right( &cells, 2);
rotate_right( &cells, 2);
// cell_1->4, 2->1, 3->2 and 4-> 3
Example Files:
None
Also See:
rotate_left(), shift_left(), shift_right()
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I see CCS C Compiler has got.
_________________
GOOD TODAY IS ENEMY OF BETTER TOMORROW |
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albe01
Joined: 02 Jul 2010
Posts: 30
Location: italy
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| Posted: Fri Jul 16, 2010 11:35 am |
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| ok but I do not understand the code replacement :( |
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albe01
Joined: 02 Jul 2010
Posts: 30
Location: italy
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| Posted: Fri Jul 16, 2010 11:52 am |
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this is the complete function:
| Code: |
//------------------------------------------------------- FUNCT FCSCHECK OK
short fcscheck(){ //computes the fcs
int i,k,bt,inbyte, fcslo, fcshi;
fcslo=fcshi=0xFF; //intialize FCS values
for (i = 0;i<(numbyte-2);i++){ //calculate the FCS for all except the last two bytes
inbyte = bte[i];
for(k=0;k<8;k++){ //perform this procedure for each bit in the byte
bt = inbyte & 0x01;
#asm
BCF STATUS,C
RRCF fcshi,F
RRCF fcslo,F
#endasm
if (((status & 0x01)^(bt)) ==0x01){
fcshi = fcshi^0x84;
fcslo = fcslo^0x08;
} //end of if
rotate_right(&inbyte,1); //set up to do the next bit
} //end of for
}
fcslo = fcslo^0xff;
fcshi = fcshi^0xff;
if ((bte[numbyte-1] == fcshi) && (bte[numbyte-2] == fcslo)) {
return 1;
}
else return 0; //if the computed values equal the last two data bytes
} //return a 1, otherwise return a 0
//------------------------------------------- VOID PRINTOUT OK
void printout(){ //function to display the received packet
int L,m; //int L,m;
for (m=7;m<13;m++){ //print the source callsign
if (bte[m] != 0x40) (putc(bte[m]>>1)); //note spaces (40) are not printed
}
putc('-');
putc(((bte[13] & 0x7F)>>1)); //print source SSID
putc('>');
for (m=0;m<6;m++){ //print the destination callsign
if (bte[m] != 0x40) (putc(bte[m]>>1));
} //end of for
putc('-');
putc(((bte[6] & 0x7F)>>1)); //print the dest SSID
L = 7;
if ((bte[13] & 0x01) != 1){ //print any path that may exist
do{
putc(',');
L=L+7;
for (m=L;m<(L+6);m++){
if (bte[m] != 0x40) (putc(bte[m]>>1));
} //end of for
putc('-');
putc(((bte[(L+6)] & 0x7F)>>1));
}while ((bte[L+6] & 0x01) != 1);
} //end of if
putc(':');
putc(' ');
L=L+9; //add 9 to move past the last callsign, cntl and PID
while (L< numbyte-2){ //print the text (not including fcs bytes)
putc(bte[L]);
L++;
} //end of while
printf("\n\r"); //add carriage return/line feed at the end
} //end of printout()
void main()
{
output_high(DCD_LED); //blink LED to know PROGRAM is running
delay_ms(1200);
output_low(DCD_LED);
printf("Test Message\r\n\n");
while (TRUE) {
get_packet();
if(fcs_check()) {
output_high(RCV_LED);
printout();
output_low(RCV_LED);
} //end if
}//end while(TRUE) loop
} //end main()
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