71M6521DH MAXIM [Maxim Integrated Products], 71M6521DH Datasheet - Page 51

• Manufacturer Part Number: 71M6521DH
• Description: Energy Meter ICs
• Manufacturer: MAXIM [Maxim Integrated Products]

71M6521DE/DH/FE Data Sheet
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.
Rev 2
CE
CE Data RAM
FIR
Analog circuits:
PLL, ADC, VREF, BME etc
MPU clock rate
MPU_DIV
ICE
DIO Pins
Watchdog Timer
LCD
EEPROM Interface (2-wire)
EEPROM Interface (3-wire)
UART
Optical TX modulation
Flash Read
Flash Page Erase
Flash Write
RAM Read and Write
Wakeup Timer
Oscillator and RTC
DRAM data preservation
V3P3D voltage output pin
Circuit Function
Table 60: Available Circuit Functions (“—“ means “not active)
System Power
(from PLL)
MISSION
4.92MHz
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
(7/8 of 32768Hz)
BROWNOUT
Yes (16kb/s)
Yes (8kb/s)
Battery Power (Non-volatile Supply)
28.672kHz
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
--
--
--
--
--
--
LCD
Yes
Yes
Yes
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
SLEEP
Yes
Yes
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
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