SLAA494B May 2011 – September 2023 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253
The background process uses the SD24 interrupt as a trigger to collect voltage and current samples (three values in total). These samples are further processed and accumulated in dedicated 48-bit registers. The background function deals mainly with timing critical events in software. After sufficient samples (one second worth) have been accumulated, the foreground function is triggered to calculate the final values of VRMS, IRMS, power, and energy. The background process is also wholly responsible for energy proportional pulses, and frequency and power factor calculation for each phase. Figure 5-2 shows the flow diagram of the background process.
The following sections discuss the various elements of electricity measurement in the background process.