新人写秒表程序出错,求解

本人在学习写两位秒表程序时出错,具体是LED一直显示两个0,秒表功能无法实现,求师傅指导,以下为我写的程序

#define EN_74HC138_ON    PORTC|=BIT(7)
#define EN_74HC138_OFF   PORTC&=~BIT(7)
typedef unsigned char uint8;
typedef unsigned int uint16;
typedef unsigned long uint32;
uint8 const number1[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};//0~9数值
uint8 number2[]={0,1,2,3,4,5,6,7};//位选0~7
uint8 units ,decade;
void I0_init(void)
{
DDRA|=0x07;
PORTA|=0x07;

DDRB=0xff;
PORTB=0xff;

DDRC|=BIT(7);
EN_74HC138_ON;
}
void time1_init(void)
{
TCCR1B|=0x02;//8分频,片内1M晶振
TCNT1H=0xcf;//(65536-(1000000/8)*0.1)/256;//每100MS溢出
TCNT1L=0x2c;//(65536-(1000000/8)*0.1)/256;
TIMSK=0x04;//TIMSK|=TOIE1;
SREG|=BIT(7);
}
void main(void)
{
I0_init();
Time0_init();
while(1)
{
  PORTA=number2[0];
  PORTB=number1[units];
  PORTA=number2[1];
  PORTB=number1[decade];
}
}
#pragma interrupt_handler Time1_init_isr:9
void Time1_init_isr(void)
{
uint8 count;
uint16 second;
TCNT1H=0xcf;//(65536-(1000000/8)*0.1)/256;
TCNT1L=0x2c;//(65536-(1000000/8)*0.1)/256;
count++;
if(count==10)
{
  count=0;
  second++;
  if(second==100)
  {
   second=0;
  }
  units=second%10;
  decade=second/10%10;
}
}