Datasheet

71M6521DE/DH/FE Data Sheet
Page: 72 of 107 Rev 3
Crystal Oscillator
The oscillator of the 71M6521DE/DH/FE drives a standard 32.768kHz watch crystal. The oscillator has been
designed specifically to handle these crystals and is compatible with their high impedance and limited power handling
capability. The oscillator power dissipation is very low to maximize the lifetime of any battery backup device attached
to VBAT.
Board layouts with minimum capacitance from XIN to XOUT will require less battery current. Good layouts will have
XIN and XOUT shielded from each other.
Since the oscillator is self-biasing, an external resistor must not be connected across the crystal.
Flash Programming
Operational or test code can be programmed into the flash memory using either an in-circuit emulator or the Teridian
Flash Programmer Module (TFP-1). The flash programming procedure uses the E_RST, E_RXTX, and E_TCLK pins.
MPU Firmware Library
All application-specific MPU functions mentioned above under “Application Information” are available as a standard
ANSI C library and as ANSI “C” source code. The code is available as part of the Demonstration Kit for the
71M6521DE/DH/FE IC. The Demonstration Kits come with the 71M6521DE/DH/FE IC preprogrammed with demo
firmware mounted on a functional sample meter PCB (Demo Board). The Demo Boards allow for quick and efficient
evaluation of the IC without having to write firmware or having to supply an in-circuit emulator (ICE).
Meter Calibration
Once the Teridian 71M6521DE/DH/FE energy meter device has been installed in a meter system, it has to be
calibrated for tolerances of the current sensors, voltage dividers and signal conditioning components. The device can
be calibrated using the gain and phase adjustment factors accessible to the CE. The gain adjustment is used to
compensate for tolerances of components used for signal conditioning, especially the resistive components. Phase
adjustment is provided to compensate for phase shifts introduced by the current sensors.
Due to the flexibility of the MPU firmware, any calibration method, such as calibration based on energy, or current
and voltage can be implemented. It is also possible to implement segment-wise calibration (depending on current
range).
The 71M6521DE/DH/FE supports common industry standard calibration techniques, such as single-point (energy-
only), multi-point (energy, Vrms, Irms), and auto-calibration.