71M6521DE Datasheet, PDF (58/101 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521DE/71M6521FE
Energy Meter IC
DATASHEET
JANUARY 2008
Data Flow
The data flow between CE and MPU is shown in Figure 26. In a typical application, the 32-bit compute engine (CE) sequen-
tially processes the samples from the voltage inputs on pins IA, VA, IB, and VB, performing calculations to measure active
power (Wh), reactive power (VARh), A²h, and V²h for four-quadrant metering. These measurements are then accessed by the
MPU, processed further and output using the peripheral devices available to the MPU.
Pulses
Samples
CE
Pre-
Processor
IRQ
Data
MPU
Post-
Processor
Processed
Metering
Data
I/O RAM (Configuration RAM)
Figure 26: MPU/CE Data Flow
CE/MPU Communication
Figure 27 shows the functional relationship between CE and MPU. The CE is controlled by the MPU via shared registers in the
I/O RAM and by registers in the CE DRAM. The CE outputs two interrupt signals to the MPU: CE_BUSY and XFER_BUSY,
which are connected to the MPU interrupt service inputs as external interrupts. CE_BUSY indicates that the CE is actively
processing data. This signal will occur once every multiplexer cycle. XFER_BUSY indicates that the CE is updating data to the
output region of the CE DRAM. This will occur whenever the CE has finished generating a sum by completing an accumulation
interval determined by SUM_CYCLES * PRE_SAMPS samples. Interrupts to the MPU occur on the falling edges of the
XFER_BUSY and CE_BUSY signals.
VAR (DIO7)
PULSES
W (DIO6)
ADC
Mux Ctrl.
SAMPLES
CE
APULSEW
APULSER
EXT_PULSE
SAG CONTROL
MPU
DATA
CE_BUSY
XFER_BUSY
INTERRUPTS
DISPLAY (me-
mory-mapped
LCD segments)
SERIAL
(UART0/1)
EEPROM
(I2C)
DIO
I/O RAM (CONFIGURATION RAM)
Figure 27: MPU/CE Communication
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