请教ADC内部温度传感器的例程问题

#include  <msp430x14x.h>

#define ADCDeltaOn       12                 // ~2 Deg C delta

static unsigned int FirstADCVal;            // holds 1st ADC result

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog
  P1OUT = 0x00;                             // Clear P1
  P1DIR = 0x01;                             // P1.0 as output
  ADC12CTL1 = SHS_1 + SHP + CONSEQ_2;       // TA trig., rpt conv.
  ADC12MCTL0 = SREF_1 + INCH_10;            // Channel A10, Vref+
  ADC12IE = 0x01;                           // Enable ADC12IFG.0
  ADC12CTL0 = SHT0_8 + REF2_5V + REFON + ADC12ON + ENC; // Config ADC12
  TACCTL1 = OUTMOD_4;                       // Toggle on EQU1 (TAR = 0)
  TACTL = TASSEL_2 + MC_2;                  // SMCLK, cont-mode
  while (!(0x01 & ADC12IFG));               // First conversion?
  FirstADCVal = ADC12MEM0;                  // Read out 1st ADC value
  _BIS_SR(LPM0_bits + GIE);                 // Enter LPM0 w/ interrupt
}

#pragma vector=ADC_VECTOR
__interrupt void ADC12ISR (void)
{
  if (ADC12MEM0 <= FirstADCVal + ADCDeltaOn)
      P1OUT &= ~0x01;                       // LED off
  else P1OUT |= 0x01;                       // LED on
}

请问“ADC12MEM0 <= FirstADCVal + ADCDeltaOn”这句是什么意思？为什么要加上12？

还有SHS_1选择定时器A触发采样，而“TACCTL1 = OUTMOD_4; ”选择toggle又是什么意思？

这个程序时测量芯片内部的温度吗？