71M6543F/H and 71M6543G/GH Data Sheet
Table 46 shows the I/O RAM registers used for temperature and battery measurement.
If TEMP_PWR selects VBAT_RTC when the battery is nearly discharged, the temperature
measurement may not finish. In this case, firmware may complete the measurement by selecting
V3P3D (TEMP_PWR = 1).
Table 46: I/O RAM Registers for Temperature and Battery Measurement
Name
Location Rst
Wk Dir Description
Indicates that hardware is still writing the 0x28A0
TBYTE_BUSY
28A0[3]
0
0
0
–
R
byte. Additional writes to this byte are locked out
while it is one. Write duration could be as long as 6 ms.
Sets the period between temperature measurements.
Automatic measurements can be enabled in any
mode (MSN, BRN, LCD, or SLP).
Time
TEMP_PER
TEMP_PER[2:0]
28A0[2:0]
R/W
Manual updates (see TEMP_START)
2 ^ (3+TEMP_PER) (seconds)
Continuous
0
1-6
7
Causes VBAT to be measured whenever a
temperature measurement is performed.
TEMP_BAT
28A0[4]
28B4[6]
0
0
–
–
R/W
R/W
TEMP_PER[2:0] must be zero in order for TEMP_START
to function. If TEMP_PER[2:0] = 0, then setting
TEMP_START starts a temperature measurement.
Ignored in SLP and LCD modes. Hardware clears
TEMP_START when the temperature measurement is
complete.
TEMP_START
Selects the power source for the temperature sensor:
1 = V3P3D, 0 = VBAT_RTC. This bit is ignored in
SLP and LCD modes, where the temperature sensor is
always powered by VBAT_RTC.
TEMP_PWR
TEMP_BSEL
28A0[6]
28A0[7]
0
0
–
–
R/W
R/W
Selects which battery is monitored by the
temperature sensor: 1 = VBAT, 0 = VBAT_RTC
Test bits for the temperature monitor VCO.
TEMP_TEST must be 00 in regular operation. Any
other value causes the VCO to run continuously with
the control voltage described below.
TEMP_TEST[1:0]
2500[1:0]
0
–
R/W
Function
TEMP_TEST
00
01
1X
Normal operation
Reserved for factory test
Reserved for factory test
STEMP[10:3]
STEMP[2:0]
2881[7:0]
2882[7:5]
R
R
The result of the temperature measurement.
The STEMP[10:0] value may be obtained in C with a
single 16-bit read and divide by 32 operation as
follows:
volatile int16_t xdata STEMP _at_0x2881;
fa = (float)(STEMP/32);
BSENSE[7:0]
BCURR
2885[7:0]
2704[3]
–
0
–
0
R
The result of the battery measurement.
Connects a 100 µA load to the battery selected by
TEMP_BSEL.
R/W
2.5.6 71M6xx3 Temperature Sensor
56 © 2008–2011 Teridian Semiconductor Corporation
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