71M6533 Datasheet, PDF (59/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

FDS_6533_6534_004
71M6533/G/H and 71M6534/H Data Sheet
2.3.1 BROWNOUT Mode
In BROWNOUT mode, most non-metering digital functions are active (as shown in Table 50) 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 processor
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 7/8 of the crystal clock rate in BROWNOUT mode. This permits the UARTs to be
operated at 300 bd. In this mode, the MPU clock has substantial short-term jitter.
The value of MPU_DIV[2:0] will be remembered (not changed) as the part enters and exits BROWNOUT.
MPU_DIV[2:0] will be ignored during BROWNOUT.
While PLL_OK = 0, the I/O RAM bits ADC_E and CE_E are held in the zero state disabling both the ADC and
the CE. When PLL_OK falls, the CE program counter is cleared immediately and all FIR processing halts.
Figure 25 shows the functional blocks active in BROWNOUT mode.
2.3.2 LCD Mode
In LCD mode, the data contained in the LCD_SEGn[3:0] fields is displayed. Up to four LCD segments
connected to the pin SEG18 can be made to blink without the involvement of the MPU, which is disabled
in LCD mode. To minimize power, only segments that might be used should be enabled.
LCD mode can be exited only by system power up, a timeout of the wake-up timer, or a push button.
When the IC exits LCD mode, the MPU can discover the event that caused the exit by reading the interrupt
flags and interpret them as follows:
• IE_WAKE = 1 indicates that the wake timer has expired.
• IE_PB =1 indicates that the pushbutton input (PB) was activated.
• COMPSTAT = 0 indicates that a reset occurred but that main power is not yet available.
• If none of the above conditions applies, system power (V3P3SYS) must have been restored
After the transition from LCD mode to MISSION or BROWNOUT mode, the PC will be at 0x0000, the
XRAM is in an undefined state, and the I/O RAM is only partially preserved (see the description of I/O
RAM states in Section 5.2). GP0[7:0] through GP7[7:0] are preserved unless a hardware reset occurs
(RESET pin is pulled high or power to the part is cycled without a battery being present). Figure 26
shows the functional blocks active in LCD mode.
2.3.3 SLEEP Mode
In SLEEP mode, the battery current is minimized and only the Oscillator and RTC functions are active.
This mode can be exited only by system power-up, a timeout of the wake-up timer, or a push button event.
When the IC exits SLEEP mode, the MPU can discover the event that caused the exit by reading the
interrupt flags and interpret them as follows:
• IE_WAKE = 1 indicates that the wake timer has expired.
• IE_PB =1 indicates that the pushbutton input (PB) was activated.
• COMPSTAT = 0 indicates that a reset occurred but that main power is not yet available.
• If none of the above conditions applies, system power (V3P3SYS) must have been restored
After the transition from SLEEP mode to MISSION or BROWNOUT mode the PC will be at 0x0000, the
XRAM is in an undefined state, and the I/O RAM is only partially preserved (see the description of I/O
RAM states in Section 5.2). GP0[7:0] through GP7[7:0] are preserved unless the a hardware reset occurs
(RESET pin is pulled high or power to the part is cycled without a battery being present). Figure 27
shows the functional blocks active in SLEEP mode.
Rev 2
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