terciof
Joined: 07 Jul 2005
Posts: 3
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| Bitwise exclusive OR |
 Posted: Thu Dec 01, 2005 7:22 pm |
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Hi All.
I Have a var called MedicaoAtual, it will hold only 1 or 0. I declared this as int1, but...:
When I bitwise exclusive OR with it, the compiler generate a lot of code for just a exclusive OR. But if the var is declared as int only two instructions.
.................... MedicaoAtual ^= 1; <-- As int1
0788: MOVLW 00
0789: BTFSC 3E.1
078A: MOVLW 01
078B: XORLW 01
078C: MOVWF 78
078D: BTFSC 78.0
078E: GOTO 791
078F: BCF 3E.1
0790: GOTO 792
0791: BSF 3E.1
...
I need to verify this variable, if it's 1 PORTB.1 = 1 and PORTB.2 = 0, when it is 0, PORTB.1 = 0 and PORTB.2 = 1.
So, what is the best solution for this, I try a lot of possibilities like:
1:
| Code: | output_bit(PIN_B1, MedicaoAtual);
output_bit(PIN_B2, input_state(PIN_B1)^1);
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2:
| Code: | output_bit(PIN_B1, MedicaoAtual);
output_bit(PIN_B2, MedicaoAtual^1);
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3:
| Code: | if(MedicaoAtual == 0)
{
output_low(PIN_B1);
output_high(PIN_B2);
}
else
{
output_high(PIN_B1);
output_low(PIN_B2);
}
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All those methods works, but which one is the best one?
Thanks all.
Tercio |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 01, 2005 7:31 pm |
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| Quote: | When I bitwise exclusive OR with it, the compiler generate a lot of code for just a exclusive OR. But if the var is declared as int only two instructions.
.................... MedicaoAtual ^= 1; <-- As int1
0788: MOVLW 00
0789: BTFSC 3E.1
078A: MOVLW 01
078B: XORLW 01
078C: MOVWF 78
078D: BTFSC 78.0
078E: GOTO 791
078F: BCF 3E.1
0790: GOTO 792
0791: BSF 3E.1 |
You want to invert an int1 variable ? Try this method:
| Code: |
int1 MedicaoAtual;
MedicaoAtual = !MedicaoAtual;
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Here is the ASM listing. It does an XOR with 1 on the specific bit.
| Code: |
0000 00504 ....
0000 00505 .... MedicaoAtual = !MedicaoAtual;
0091 3001 00506 MOVLW 01
0092 06AB 00507 XORWF 2B,F |
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