stepper.c 
stepper.hex 

/* 
* STEPPER.C 
* sweeping stepper's rotor cw and cww 400 steps 
* Copyright (c) 1999 by W.Sirichote 
*/ 

#include c:\mc51\8051io.h /* include i/o header file */ 
#include c:\mc51\8051reg.h 

register unsigned char j,flag1,temp; 
register unsigned int cw_n,ccw_n; 

unsigned char step[8]={0x80,0xc0,0x40,0x60,0x20,0x30,0x10,0x90} 
#define n 400 

/* flag1 mask byte 
0x01 run cw() 
0x02 run ccw() 
*/ 

main() 

{ 
flag1=0; 
serinit(9600); 
disable(); /* no need timer interrupt */ 
cw_n = n; /* initial step number for cw */ 
flag1 |=0x01; /* initial enable cw() */ 

while(1){ 
{ 
tick_wait(); /* wait for 10ms elapsed */ 

energize(); /* round-robin execution the following tasks every 10ms */ 
cw(); 
ccw(); 
} 
} 

} 

cw(){ 
if((flag1&0x01)!=0) 
{ 
cw_n--; /* decrement cw step number */ 
if (cw_n !=0) 
j++; /* if not zero increment index j */ 
else 
{flag1&=~0x01; /* disable cw() execution */ 
ccw_n = n; /* reload step number to ccw counter */ 
flag1 |=0x02; /* enable cww() execution */ 
} 
} 

} 

ccw(){ 
if((flag1&0x02)!=0) 
{ 
ccw_n--; /* decremnent ccw step number */ 
if (ccw_n !=0) 
j--; /* if not zero decrement index j */ 
else 
{flag1&=~0x02; /* disable ccw() execution */ 
cw_n = n; /* reload step number to cw counter */ 
flag1 |=0x01; /* enable cw() execution */ 
} 
} 

} 

tick_wait(){ /* cputick was replaced by simpler ASM code 10ms wait */ 

asm" JNB TCON.5,*"; /* wait for TF0 set */ 
asm" CLR TCON.5"; /* clear TF0 for further set */ 
asm" ORL TH0,#$DC"; /* reload TH0 with $DC, TL0 = 0 */ 
} 

energize(){ 

P1 = step[(j&0x07)]; /* only step 0-7 needed */ 
}