On your code,

P1MDOUT = 0xC0; // set P1.7, P1.6 to push-pull
...
XBR1 = 0x40;    // enable crossbar - output drivers on ports are enabled, too

If P1.7 or P1.6 accidentally short to GND, or if these ports conflict with output of other component,
short current may disturb VDD supply at "XBR1 = 0x40;" timing.
What do P1.7 / P1.6 connect to?

void Timer_Init()
{
TCON = 0x51; //INT0 is edge triggered ,Timer0/1 is enable
TMOD = 0x12;
CKCON = 0x02;
TL1 = 0x4F;
TH1 = 0x9C;
}

void SMBus_Init()
{
SMB0CF = 0x80;//enable SMBus
}

void ADC_Init()
{
ADC0MX = 0x0B;
ADC0CF = 0x18;//
ADC0CN = 0x80;
}

void DAC_Init()
{
IDA1CN = 0xF4;//0.25mA
IDA0CN = 0xF4;//0.25mA

}

void Voltage_Reference_Init()
{
REF0CN = 0x17;
}

void Port_IO_Init()
{
// P0.0 - SDA (SMBus), Open-Drain, Digital
// P0.1 - SCL (SMBus), Open-Drain, Digital
// P0.2 - Skipped, Open-Drain, Digital
// P0.3 - Skipped, Open-Drain, Digital
// P0.4 - Skipped, Open-Drain, Digital
// P0.5 - Skipped, Open-Drain, Digital
// P0.6 - Skipped, Open-Drain, Digital
// P0.7 - Skipped, Open-Drain, Digital

// P1.0 - Skipped, Open-Drain, Digital
// P1.1 - Skipped, Open-Drain, Analog
// P1.2 - Skipped, Open-Drain, Digital
// P1.3 - Skipped, Open-Drain, Analog
// P1.4 - Skipped, Open-Drain, Digital
// P1.5 - Skipped, Open-Drain, Digital
// P1.6 - Skipped, Open-Drain, Digital
// P1.7 - Skipped, Open-Drain, Digital

// P2.0 - Skipped, Open-Drain, Digital
// P2.1 - Skipped, Open-Drain, Digital
// P2.2 - Skipped, Open-Drain, Digital
// P2.3 - Skipped, Open-Drain, Digital
// P2.4 - Skipped, Open-Drain, Digital
// P2.5 - Skipped, Open-Drain, Digital
// P2.6 - Skipped, Open-Drain, Digital
// P2.7 - Skipped, Open-Drain, Digital

P2MDIN = 0xF8; //P2.0,P2.1,P2.2 Analog input
P2SKIP = 0x07;
P2 = 0xFF;
P1MDIN = 0xF7;//P1.3 Analog input
P1SKIP = 0x08;
P1MDOUT = 0xC0;
P0MDOUT = 0x00;
P0 = 0xFF;
P0SKIP = 0x83;
XBR1 = 0x40;
XBR0 = 0x04;

}

void Oscillator_Init()
{
int i = 0;
OSCICN = 0x87;
}

void Interrupts_Init()
{ IT01CF = 0x07; //INT0 PIN is P0.7
EIE1 = 0x01;//enable SMBus interrupt
EIP1 = 0x01;//SMBus interrupt high
IE = 0x01;//enable INT0 interrupt EA=0 ,disable Timer1 interrupt
IP = 0x00;//INT0 interrupt low

}