71M6521BE
Energy Meter IC
DATA SHEET
JANUARY 2008
CK32
MUX_SYNC
CKTEST
0
1
30 31
0
1
30 31
0
1
30 31
0
1
30 31
TMUXOUT/RTM
FLAG
FLAG
FLAG
FLAG
RTM DATA0 (32 bits)
RTM DATA1 (32 bits)
RTM DATA2 (32 bits)
RTM DATA3 (32 bits)
Figure 17: RTM Output Format
Battery Modes
Shortly after system power (V3P3SYS) is applied, the part will be in MISSION mode. MISSION mode means that the part is
operating with system power and that the internal PLL is stable. This mode is the normal operation mode where the part is
capable of measuring energy.
When system power is not available (i.e. when V1<VBIAS), the 71M6521DE/FE can be in one of three battery modes, i.e.
BROWNOUT, LCD, or SLEEP mode. As soon as V1 falls below VBIAS or when the part wakes up under battery power (with
sufficient voltage margin), the part will automatically enter BROWNOUT mode (see Wake Up Behavior section). From
BROWNOUT mode, the MPU may enter either LCD mode or SLEEP mode by setting either the LCD_ONLY or SLEEP I/O RAM
bits (only one bit can be set at the same time in BROWNOUT mode, since setting one bit will already force the part into SLEEP
or LCD mode, disabling the MPU).
Figure 18 shows a state diagram of the various operation modes, with the possible transitions between modes. For information
on the timing of mode transitions refer to Figure 22 through Figure 24.
When V1 falls below VBIAS or the part wakes up under battery power, the part will automatically enter BROWNOUT mode
(see Wake Up Behavior section). From BROWNOUT mode, the part may choose to enter either LCD mode or SLEEP mode,
as controlled by the MPU via the I/O RAM bits LCD_ONLY and SLEEP.
Meters that do not require functionality in the battery modes still need to contain code that brings the chip from
BROWNOUT mode to SLEEP mode. Otherwise, the chip remains in BROWNOUT mode, once the system power is
missing, and consumes more current than intended.
Similarly, meters equipped with batteries need to contain code that transitions the chip to SLEEP mode as soon as the
battery is attached in production. Otherwise, remaining in BROWNOUT mode would add unnecessary drain to the
battery.
The transition from MISSION mode to BROWNOUT mode is signaled by the IE_PLLFALL interrupt flag (in SFR 0xE8[7]). The
transition in the other direction is signaled by the IE_PLLRISE interrupt flag (SFR 0xE8[6]), when the PLL becomes stable.
Transitions from both LCD and SLEEP mode are initiated by wake-up timer timeout conditions or pushbutton events. When the
PB pin is pulled high (pushbutton is pressed), the IE_PB interrupt flag (SFR 0xE8[4]) is set, and when the wake-up timer times
out, the IE_WAKE interrupt flag (SFR 0xE8[5]) is set.
In the absence of system power, if the voltage margin for the LDO regulator providing 2.5V to the internal circuitry becomes too
low to be safe, the part automatically enters sleep mode (BAT_OK false). The battery voltage must stay above 3V to ensure
that BAT_OK remains true. Under this condition, the 71M6521BE stays in SLEEP mode, even if the voltage margin for the
LDO improves (BAT_OK true).
Table 59 shows the circuit functions available in each operating mode.
V1.0
© 2005-2008 TERIDIAN Semiconductor Corporation
Page: 49 of 97
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