71M6515H Datasheet, PDF (27/57 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6515H
Energy Meter IC
DATA SHEET
MARCH 2008
Meter Design - Scaling of Measured Values
An actual meter will always use sensors that scale the voltages and currents managed by the meter to small voltages that can
be processed by the 71M6515H. This scaling is reflected in the system parameters VMAX and IMAX. Scaling is physically
implemented with resistor dividers for the voltage signals and current transformers, shunt resistors or Rogowski coils for the
current signals.
IMAX is the RMS meter current that results in 250mV peak signal (or 177mV RMS) at the ADC input (IA, IB, IC pins). VMAX is
the RMS meter voltage that results in 250mV peak signal at the ADC input (VA, VB, VC pins). In_8 is either 1 or 8, depending
on In_8x, the ADC gain configuration bit for element n (see IA_8, IB_8, IC_8) in the CONFIG register.
Only the host is aware of the system parameters VMAX and IMAX, while the CE and the post-processor know signal
amplitudes only as values relative to their maximum peak levels (250mV). This makes the host itself responsible for translating
the measured values from the 71M6515H registers into real-world values by applying the parameters VMAX, IMAX and In_8.
Equally, the host is responsible for non-volatile storage of accumulated energy values, calibration factors, default settings et
cetera.
Measured values and values determining the function of the 71M6515H, as controlled by the registers described in the
following section, are often stated as fractions or multiples of the system parameters VMAX, IMAX and In_8.
Host Interface - REGISTER DESCRIPTION
Communication between the host and the 71M6515H is established by writing to and reading from the registers described in
this section. The registers are accessible via the UART (see UART Write and Read Operation).
The tables below contain the registers that can be accessed by the host to obtain data from the 71M6515H or to control and
configure the IC.
Bits with a W (write) direction are written by the host. Bits with R (read) direction can only be read by the host. Write operations
attempted to read-only registers will result in the CMD_IGNORED bit set in the STATUS register. Unless stated otherwise, all
registers are four bytes (32 bits), 2’s complement, and have a range of (2³¹-1) to -(2³¹-1).
Register Groups
Each register belongs to one of the following functional groups:
• Pulse Generation
• Calibration
• Control of Basic Functions
• Temperature
• Temperature Compensation
• Output Signals
• Accumulated Energy and V/I Values
• Alarms and Thresholds
• Time (RTC)
• Test
• Digital I/O Control (pins D0…D7)
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