71M6521DE/71M6521FE
Energy Meter IC
DATASHEET
JANUARY 2008
System Power
MISSION
Battery Power (Non-volatile Supply)
Circuit Function
BROWNOUT
LCD
SLEEP
CE
Yes
Yes
Yes
--
Yes
--
--
--
--
--
--
--
CE Data RAM
FIR
Analog circuits:
PLL, ADC, VREF, BME etc
Yes
--
--
--
--
--
4.92MHz
(from PLL)
Yes
28.672kHz
MPU clock rate
(7/8 of 32768Hz)
MPU_DIV
--
Yes
--
--
--
--
--
--
--
--
--
--
ICE
Yes
DIO Pins
Yes
Yes
--
Watchdog Timer
LCD
Yes
Yes
--
Yes
Yes
Yes
--
EEPROM Interface (2-wire)
EEPROM Interface (3-wire)
UART
Yes
Yes (8kb/s)
Yes (16kb/s)
Yes
Yes
--
Yes
--
Optical TX modulation
Flash Read
Flash Page Erase
Flash Write
Yes
Yes
Yes
Yes
Yes
--
--
--
--
--
--
--
--
--
--
--
Yes
Yes
--
RAM Read and Write
Yes
Wakeup Timer
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
--
Yes
Yes
--
Oscillator and RTC
DRAM data preservation
V3P3D voltage output pin
--
--
Table 60: Available Circuit Functions (“—“ means “not active)
BROWNOUT Mode
In BROWNOUT mode, most non-metering digital functions, as shown in Table 60, are active, including ICE, UART, EEPROM,
LCD, and RTC. In BROWNOUT mode, a low bias current regulator will provide 2.5 Volts to V2P5 and V2P5NV. The regulator
has an output called BAT_OK to indicate that it has sufficient overhead. When BAT_OK = 0, the part will enter SLEEP mode.
From BROWNOUT mode, the MPU can voluntarily enter LCD or SLEEP modes. When system power is restored, the part will
automatically transition from any of the battery modes to mission mode, once the PLL has settled.
The MPU will run at crystal clock rate in BROWNOUT. The value of MPU_DIV will be remembered (not changed) as the part
enters and exits BROWNOUT. MPU_DIV will be ignored during BROWNOUT.
While PLL_OK = 0, the I/O RAM bits ADC_E and CE_E are held in zero state disabling both ADC and CE. When PLL_OK falls,
the CE program counter is cleared immediately and all FIR processing halts. Figure 19 shows the functional blocks active in
BROWNOUT mode.
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© 2005-2008 TERIDIAN Semiconductor Corporation
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TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
