AD Sampling of ADuc7039 Chip Needs External Reset,how to solve it?

When I using ADUC7039, Iam found that the system needs external reset after power Down or restart, otherwise the sampling voltage acquisition is incorrect.

By observing that the AD sampling voltage acquisition is twice the correct value, (For example, after resetting aduc7039, the AD sampling value is 3.1V, while the non-resetting AD sampling value is 6.2V)we checked the manual to find out what is the reason, and it can not be solved by software reset.

I don't know if the parameter configuration is incorrect or if there are other configurations?

while((PLLSTA&0x2)==0) {} // Ensure That thePLL is locked to the 3%
// SysClock=20.48MHz/2=10.24MHz (POWCON:CD=1 by default)
/* Timer2 setup ADuC7039 */
T2CON = 0; // Disable watchdog timer

/* Timer0 setup ADuC7039 */
T0CON = 0x002A; // clock = SysClock/16384=625Hz, Count down, Periodic
T0LD = 625; // 625Hz/625 = 1Hz

/* ADC setup ADuC7036/39 */
//ADC0CON = 0x0001; // disable I-ADC, twos complement, gain=2
ADC1CON = 0x8200; // enable V-ADC & T-ADC, select V-ADC, uniplolar coding, internal Temp sensor
ADCFLT = 0x961f; // AF=0,SF=7,F_ADC=512KHz/(SF+1)/64=1KHz
ADCMSKI = 0x02; // enable all ADC interrupt
ADCMDE = 0x01; // ADC normal mode, continuous conversion 

/* GPIO setup ADuC7039 */
GPCON = 0x00001111; // all GPIO configured as general purpose IO ÅäÖÃΪ SPI ¿Ú
GPSET = 0x00000000; // GPSET=0 does not affect GPIO output level
GPCLR = 0x00000000; // GPCLR=0 does not affect GPIO output level
GPDAT = 0x34000000; // GPIO_2(MISO)/4/5 set as output, write 1; others GPIO_x£¨/SS, SCLK, MOSI£
SPICON = 0x0341; // 0b41 0809 bit 0x8301

/* IRQ/FIR setup */ 
IRQ = Vector_IRQ;
FIQ = Vector_FIQ;
IRQEN = 0x00000200; // Enable SPI interrupt 0x20 SPI inti 0x4: Enable Timer0 int 0x00000004
FIQEN = 0x00000100; // ADuC7039 only: Enable ADC int