Hello all,
I am working on PCB tester with programming capabilities for PIC - of course in
SDCC. I compile target.c, generated HEX is then processed into .H file and
linked together with code of the main application. Target code is really
simple, but it seems to me that overhead is quite big. I tried the simplest
code with LED blinking and SW UART (see below).
If I compile it, the main code itself has about 216bytes (taken from .LST). But
when I link it, I get around 460 bytes. With "--use-crt=crt0.o" I get around
270 bytes, it is better.
My questions are:
- Why "vectors" page is 0x00-0x29 ? Where is said, how much memory I need for
INT jumps ? I feel that 2 bytes are enough - just "goto __INT_HANDLER".
- I understand that if I don't use any interrupt, I can reduce "vectors" page
to 0x04, can't I ?
- When is it necessary to use "crt0i" instead of "crt0" ?
Thank you in advance,
Vasek
/* main.c */
/*************** pin definitions *****************/
#define LED_TRIS TRISCbits.TRISC0
#define LED_PIN LATCbits.LATC0
#define SWUART_TX_TRIS TRISBbits.TRISB6
#define SWUART_TX_PIN LATBbits.LATB6
#include <pic18fregs.h>
#pragma stack 0x300 150
__code char __at(__CONFIG1H) conf1h = 0x02; // Select HS OSC
__code char __at(__CONFIG2L) conf2l = 0x1e; // BOREN enabled, PWRTEN enabled
__code char __at(__CONFIG2H) conf2h = 0x00; // WDT disabled
__code char __at(__CONFIG3H) conf3h = 0x00; // digi RB pins, TMR1 normal
__code char __at(__CONFIG4L) conf4l = 0x81; // Disable LVP, disable ext. mode
void swuart_put( unsigned char aChar) __wparam;
void swuart_del( void);
void WWdelay (void);
/******************* main() ***********************/
void main()
{
OSCCON = 0x70;
LED_TRIS = 0;
SWUART_TX_TRIS = 0;
do {
swuart_put( 0x55);
swuart_put( 0xaa);
swuart_put('H');
swuart_put('e');
swuart_put('l');
swuart_put('l');
swuart_put('o');
swuart_put(0x0d);
WWdelay();
LED_PIN = 0;
WWdelay();
LED_PIN = 1;
} while (1);
}
/***********************************************************/
/* software UART - 9600Bd @ 10MHz */
void swuart_del()
{
unsigned char icnt2;
for( icnt2 = 0; icnt2 < 80; icnt2++) ;
}
void swuart_put( unsigned char aChar) __wparam
{
unsigned char cnt;
//INTCONbits.GIE = 0;
SWUART_TX_PIN = 0;
swuart_del();
for (cnt = 0; cnt < 8; cnt++) {
if (aChar & 0x01) {
SWUART_TX_PIN = 1;
} else {
SWUART_TX_PIN = 0;
}
aChar >>= 1;
swuart_del();
}
SWUART_TX_PIN = 1;
//INTCONbits.GIE = 1;
swuart_del();
swuart_del();
}
void WWdelay (void)
{
volatile unsigned char tmpc;
for(tmpc = 0; tmpc < 250; tmpc++) swuart_del();
}
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