Maxim Integrated 78M6631 - Manual (Page 14)

78M6631 Firmware Description Document UG_6631_078
14 Rev 2
2.3 Configuration and Control
2.3.1 Input Registers
The following parameters are configurable by the user via input registers:
• Sensor range and configuration
• Calibration targets and coefficients
• Alarm Thresholds and Mask Settings
2.3.2 Sensors Configuration
A few parameters specific to the voltage and current sensors and their connections require one time
configuration.
Sensor Output Range
The sensor’s output needs to be adapted to the ADC input range (+/- 250mVpk). In case of a Current
Transformer (CT), the burden resistor value should be selected in order to match the maximum ADC input
voltage at the maximum load current that need to be measured. Similarly consideration applies for the
voltage sensor (Voltage Dividers or Voltage Transformers).
Delta/Wye Configuration Selection
The different connections can be selected through the external dedicated D/Y pin or through commands
over the UART or SPI interfaces. At power-on or reset the D/Y pin is sampled and its status determines
the set of equations enabling the proper configuration. After the initialization, the configuration can then
be changed by the user through the command register. Bit 2 (Delta) set to 0 selects the Wye
configuration while Bit 2 set to 1 selects the Delta configuration.
The status of the Delta bit in the command register is always overwritten at power-on with the status of
the D/Y pin.
2.3.3 Updating Flash
The values of several input registers can be updated by the user at run-time. A flash update routine is
provided to save the values of various registers as default. To save the registers values to flash memory,
see the section describing the command register.
2.3.4 Scaling
Scaling registers provide a means for the user to adapt the meaning of the results to the end
application. There are separate scaling registers for RMS voltage, RMS current, power, and power
factor, but each register covers all three phases.
By default, scaling registers are set so that result LSBs represent one millivolt, milliamp, or milliwatt,
millihertz, Power factor is scaled to 1 LSB = .001.
Example
The scaling registers contain full-scale values in units selected by the user. For example, 50 amps full
scale with a resolution of 1 milliamp will be a scaling register value of 50000.