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thomasj50
Joined: 23 Aug 2006
Posts: 19
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| 'Endianness' of multibyte variables |
 Posted: Wed Aug 23, 2006 10:40 pm |
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Hi,
I seems that the CCS compiler uses 'little endian' encoding of 16 and 32 bit variables, i.e. the least significant byte is stored first (at the lowest address), which Intel/Microsoft also does. Is there anyone that can confirm this ?
Best Regards,
Thomas Johansson |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Aug 23, 2006 11:30 pm |
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You can confirm it yourself by compiling a test program and looking
at the .LST file.
| Code: | #include <16F877.h>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
//========================
void main()
{
int32 temp;
temp = 0x44332211;
while(1);
} |
Note the 0x11 is the LSB and 0x44 is the MSB.
| Code: |
.................... int32 temp;
.................... temp = 0x44332211;
000C: MOVLW 44
000D: BCF 03.5
000E: MOVWF 24
000F: MOVLW 33
0010: MOVWF 23
0011: MOVLW 22
0012: MOVWF 22
0013: MOVLW 11
0014: MOVWF 21
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From the symbol table:
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thomasj50
Joined: 23 Aug 2006
Posts: 19
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| Endianness |
| Posted: Thu Aug 24, 2006 12:18 am |
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Well, perhaps I could have confirmed it myself if I had understood the PIC assembler :-) I guess I am one of the few that went directly to C programming with this processor, after having spent 30 years digging trough assembler listings.
It is confirmed then ?
Best Regards.
Thomas J |
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libor
Joined: 14 Dec 2004
Posts: 288
Location: Hungary
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| Posted: Thu Aug 24, 2006 2:41 am |
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Yes, confirmed. You can also check it understanding pure C only:
| Code: | ...
long temp;
int *ptr;
temp = 0x2211;
ptr = &temp;
if (*ptr == 0x11) printf("LSB is stored first\r\n");
...
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future
Joined: 14 May 2004
Posts: 330
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| Posted: Tue Sep 05, 2006 8:45 pm |
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How would you solve the problem to read little endian streams mapped to a struct?
I have some programs with hard-coded offsets and I am willing to make them more readable...
Thank you. |
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