请教N76e003的ADC的Bandgap例程中的问题？

只看该作者 · 2020-12-15 09:36

现在正在学习ADC编程，阅读了“N76E003之ADC带隙电压（Band-gap）”网友介绍的这篇大作，其中读取UID后面的保存芯片中的BANDGAP值的内容不是太理解，请大家帮忙看一下：
            set_IAPEN;
IAPCN = READ_UID;
IAPAL = 0x0d;
            IAPAH = 0x00;
            set_IAPGO;
BandgapLow = IAPFD;
BandgapMark = BandgapLow&0xF0;

if (BandgapMark==0x80)
{
BandgapLow = BandgapLow&0x0F;
IAPAL = 0x0C;
IAPAH = 0x00;
set_IAPGO;
BandgapHigh = IAPFD;
Bandgap_Value = (BandgapHigh<<4)+BandgapLow;
Bandgap_Voltage_Temp = Bandgap_Value*3/4;
Bandgap_Voltage = Bandgap_Voltage_Temp - 33; //the actually banggap voltage value is similar this value.
}
if (BandgapMark==0x00)
{
BandgapLow = BandgapLow&0x0F;
IAPAL = 0x0C;
IAPAH = 0x00;
set_IAPGO;
BandgapHigh = IAPFD;
Bandgap_Value = (BandgapHigh<<4)+BandgapLow;
Bandgap_Voltage= Bandgap_Value*3/4;
}
if (BandgapMark==0x90)
{
IAPAL = 0x0E;
IAPAH = 0x00;
set_IAPGO;
BandgapHigh = IAPFD;
IAPAL = 0x0F;
IAPAH = 0x00;
set_IAPGO;
BandgapLow = IAPFD;
BandgapLow = BandgapLow&0x0F;
Bandgap_Value = (BandgapHigh<<4)+BandgapLow;
Bandgap_Voltage= Bandgap_Value*3/4;
}
clr_IAPEN;

请问上面为什么要分为三种情况处理，分别是：
            if (BandgapMark==0x80)...
            if (BandgapMark==0x00)...
            if (BandgapMark==0x90)...
???????