what's the advantage of #define set_bit_var(x) bit_set (*(in

[MICHAEL]

Hi,

In previous post, I saw macros:

#define set_bit_var(x) bit_set (*(int8 *)(x >>3), x & 7)

#define clear_bit_var(x) bit_clear (*(int8 *)(x >>3), x & 7)

#define read_bit_var(x) bit_test (*(int8 *)(x >>3), x & 7)

I am not sure the advantages of these macros, when CCS already has built-in functions to bit_set, bit_clear and bit_test.

Can some one please clarify. Thanks

[PCM programmer]

They accept a CCS-style pin number, in a variable, as the argument.
Example:

[michael]

Hi PCM Programmer,

I tried to compile some examples and the lst files are different. One is writng to the port and the other to the latach. But both perform the same function. May be just for personal prefereces. Regards.


.................... set_bit_var(pin_a0);
002A: BSF F80.0
.................... output_bit (pin_a0, 1);
002C: BSF F89.0
002E: BCF F92.0
....................
.................... clear_bit_var(pin_b0);
0030: BCF F81.0
.................... output_bit (pin_b0, 0);
0032: BCF F8A.0
0034: BCF F93.0
....................
.................... a = read_bit_var(pin_c0);
0036: BCF 06.0
0038: BTFSC F82.0
003A: BSF 06.0
.................... b = bit_test (*PORTC, 0);
003C: BCF 06.1
003E: BTFSC F82.0
0040: BSF 06.1
....................

[PCM programmer]

You're using constants as the arguments. Try it with a variable.

If you have vs. 3.249 or before, and if you plug in a variable as
the argument, you will get this compiler error message:

[michael]

Hi PCM Programmer,

I am not sure what do you mean by variable.

In the example you posted, pin = PIN_B0. PIN_B0 is 31752 (int16). when assigned to pin (int8), it becomes hex 08. When you plug it in set_bit_var (pin), it will get devided by 8 and use as an int8 pointer and get the content of it and set the bit.

Regards,



#include <16F877>
#fuses HS, NOWDT, BROWNOUT, PUT, NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

#define set_bit_var(x) bit_set (*(int8 *)(x >>3), x & 7)

//==========================
void main()
{
int8 pin;

pin = PIN_B0;

set_bit_var(pin);


while(1);
}

[PCM programmer]

This is a constant:

[michael]

Hi PCM programmer,

Thanks for the clarifications. I compiled using 18F452 and I got similar list files. It is neat the the same macro can work for both 16F and 18F devices. Still that's a lot of instructions to set a bit.

Regards

.................... set_bit_var(c);
003E: RRCF 08,W
0040: MOVWF 03
0042: RRCF 07,W
0044: MOVWF 02
0046: RRCF 03,F
0048: RRCF 02,F
004A: RRCF 03,F
004C: RRCF 02,F
004E: MOVLW 1F
0050: ANDWF 03,F
0052: MOVFF 02,FE9
0056: MOVFF 03,FEA
005A: MOVF 07,W
005C: ANDLW 07
005E: MOVWF 0D
0060: CLRF 0E
0062: MOVLW 01
0064: MOVWF 00
0066: MOVF 0D,W
0068: MOVWF 01
006A: BZ 0074
006C: BCF FD8.0
006E: RLCF 00,F
0070: DECFSZ 01,F
0072: BRA 006C
0074: MOVF 00,W
0076: IORWF FEF,F