6613_OMU_2+2S_URT_V100 Firmware Description Document

This document describes the 6613_OMU_2+2S_URT_v100 firmware, which is used with the Teridian
78M6613 power and energy measurement IC. This firmware provides simple methods for calibration and
access to measurement data such as Instantaneous Power, Voltage, Current, Power Factor, and Line
Frequency.  It is specifically developed for measurement of up to two single phase loads with the
following key features:
 
•  Optimized for using current shunt resistors with analog inputs A0, A2 are configured as Voltage input
and input A1,A3 are configured as Current inputs.  
•  Phase error calibration routine included for use of current transformers and/or maintaining accuracy
over non-ideal power factors.
•  Low-latency SAG status pin for sub-cycle AC fault detection.
•  UART (RS232) host interface (Command Line Interface).
 
All measurement calculations are computed by the 78M6613 and communicated to the host processor
over a serial interface (UART0) on the TX and RX pins of the 78M6613 device.  Digital IOs utilized by this
firmware include:
 
Figure 1 shows a simplified connection diagram of the 78M6613 (emulator connections, decoupling
capacitors and 3.3VDC power supply are omitted in this diagram).