Adding int8 slow down timing?

[fastlink30]

i use CCP compare to make 50hz square wave, the problem is if i insert the line ATT_MOT ... the signal lenght became very long (7 Hz), without this line all goes well
there are solution? optimization? or bug?
i tried many things, but when i try to add 1 to att_mot the timings became incorrect
i check frequency with proteus 7.1 sp2

i use 16f877 16mhz
ATT_MOT is int8
PCWH 4.033

thanks

#int_ccp1
void interr_ccp1() {
if (ATT_STEP) {
bit_set(PORTA_D, ATT_MOT);
ATT_TIME = MOTORI[ATT_MOT].POS_TIME;
CCP_1 = 10000;
set_timer1(0);
ATT_STEP = FALSE;
} else {
bit_clear(PORTA_D, ATT_MOT);
CCP_1 = 10000;
ATT_MOT = ++ATT_MOT % 8; <<<<----- slow down!!
set_timer1(0);
ATT_STEP = TRUE;
}
}

void main() {
int8 car;

setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_4);
setup_timer_2(T2_DISABLED,0,1);

port_b_pullups(FALSE);

set_tris_a(0b00000000);
set_tris_b(0b00000000);
set_tris_c(0b10000000);// 0 = output
set_tris_d(0b00000000);
set_tris_e(0b00000000);


CCP_1=0;
set_timer1(0);
clear_interrupt(INT_CCP1);
setup_ccp1(CCP_COMPARE_INT);
enable_interrupts(INT_CCP1);

disable_interrupts(INT_TIMER0);
disable_interrupts(INT_TIMER2);
enable_interrupts(GLOBAL);
....

[fastlink30]

the problem is ++ without that all is ok, but how can i solve?

[Neutone]

for an INT8

ATT_MOT = ++ATT_MOT % 8; <<<<----- slow down!!

can be re written as

++ATT_MOT;
bit_Clear(ATT_MOT,3);

This assumes that this is the only place that the value will be incremented.

Also try

++ATT_MOT;
ATT_MOT=ATT_MOT%8;

[fastlink30]

thank you for your reply but not solved! :(

already tried this
att_mot++;
ATT_MOT %= NUM_MOTORI;

the problem is the addiction if i leave the ++ all goes ok, if i try to do:

att_mot += 1; or
att_mot = att_mot+1;

the problem is always the same! if i look ASM

.................... CCP_1 = CICLE_LEN - ATT_TIME;
0141: MOVF 2C,W
0142: SUBWF 29,W
0143: MOVWF 15
0144: MOVF 2A,W
0145: MOVWF 16
0146: MOVF 2D,W
0147: BTFSS 03.0
0148: INCFSZ 2D,W
0149: SUBWF 16,F
.................... att_mot++;
014A: INCF 2B,F
.................... ATT_MOT %= NUM_MOTORI;
014B: MOVLW 07
014C: ANDWF 2B,F

if seem correct (i don't know exactly pic assembler)

what can be the problem? memory bank?

[PCM programmer]

The reason the rate of the output signal is lower is because you're
now changing 8 pins, instead of just one pin.
The original output frequency for just one pin was 50 Hz. When you
change the code so that pin is only updated one time in 8, compared
to before, the new frequency for that pin will become 50 Hz / 8 = 6.5 Hz.
That's because each pin is updated only 1/8th as often as before.

[fastlink30]

thank for the reply

sorry for stupid question!