atmel89s8252 problem to display in lcd

the problem i ask yesterday hv solved, the now i'm facing another prob. which is the velocity value cant display in LCD once i reach "START==0 AND STOP==0" it will display 255 for the velocity value, could anyone help me with that, thanks alot

#include <AT898252.H>
#include <stdio.h>
#include "LCD.c"
unsigned char pulse_low=0,pulse_high=0;
unsigned int overflow_count=0,int_count=1,pulse=0,time=0;
unsigned int velocity=0;
unsigned long int pulse_width=0;
unsigned char b;
sbit START=P1^0;
sbit STOP=P1^1;
char buf[16];
void main(){
        lcd_init();
        lcd_puts("The Speed Is");
        msdelay(1000);
        TMOD=0x90;
        TF1=0;
        IT1=1;
        IE=0x8c;
        while(1){
                unsigned char a;
        //      unsigned char x;
                if(START==0&&STOP==1){
                        a=0;
                }
                else if(START==1&&STOP==0){
                        a=2;
                }
                else if(START==1&&STOP==1){
                        a=3;
                }
                else if (START==0&&STOP==0){
                        a=1;
                }

                switch(a){
                        case 0:{
                                TR1=1;
                                break;
                        }

                        case 1:{
                                pulse_low=TL1;
                                pulse_high=TH1;
                                pulse=(TH1<<8)+TL1;
                                pulse_width=(overflow_count)*65536+pulse;
                                time=pulse_width/13921583;
                                velocity=(180/time);
                                lcd_gotoxy(0,1);
                                lcd_putchar(' ');
                                sprintf(buf,"%u",v);
                                lcd_puts(buf);
                                break;
                        }
                        case 2:{
                                TR1=0;
                                TH1=0x00;
                                TL1=0x00;
                                overflow_count=0;
                                break;
                        }
                        default:{
                                break;

                        }
                }
        }
}
void timer1_int()interrupt 3
{
 overflow_count++;
}