请问 N76E003 内部带隙电压(band-gap voltage)恒定为1.22V吗？

现在按照1.22V，程序计算的的结果与实际电压有偏差。。另外“ADC_Bandgap_VDD”这段DEMO程序计算band-gap voltage的方法有点看不明白，规格书相关的东西，也没有详细说明。但通过这个代码来看，band-gap voltage好像不是恒定的啊。有些困惑，请求帮助。

void READ_BANDGAP()

{

UINT8 BandgapHigh,BandgapLow;

double Bandgap_Value;

set_IAPEN;

IAPAL = 0x0C;

    IAPAH = 0x00;

    IAPCN = READ_UID;

    set_IAPGO;

BandgapHigh = IAPFD;

IAPAL = 0x0d;

    IAPAH = 0x00;

    IAPCN = READ_UID;

    set_IAPGO;

BandgapLow = IAPFD;

BandgapLow = BandgapLow&0x0F;

clr_IAPEN;

Bandgap_Value = (BandgapHigh<<4)+BandgapLow;

Bandgap_Voltage = 3072/(0x0fff/Bandgap_Value);

}