71M6545 Datasheet, PDF (54/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

Data Sheet 71M6545/H
PDS_6545_009
Table 43: I/O RAM Registers for Temperature and Battery Measurement
Name
Location Rst Wk Dir Description
TBYTE_BUSY
Indicates that hardware is still writing the 0x28A0
28A0[3] 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.
TEMP_PER[2:0] 28A0[2:0] 0
Sets the period between temperature measurements.
Automatic measurements can be enabled in any
mode (MSN and during ac power outages if the
VBAT_RTC voltage is within specification, as
– R/W ^{supplied by a battery).}
TEMP_PER Time
0
Manual updates (see TEMP_START)
1-6
2 ^ (3+TEMP_PER) (seconds)
7
Continuous
TEMP_BAT
28A0[4]
0
–
R/W
Causes the VBAT_RTC pin to be measured
whenever a temperature measurement is performed.
TEMP_START
TEMP_PER[2:0] must be zero in order for TEMP_START
to function. If TEMP_PER[2:0] = 0, then setting
28B4[6]
0
–
R/W
TEMP_START starts a temperature measurement.
This bit is ignored in SLP mode. Hardware clears
TEMP_START when the temperature measurement is
complete.
TEMP_PWR
Selects the power source for the temperature sensor:
28A0[6]
0
–
R/W
1 = V3P3D, 0 = VBAT_RTC. This bit is ignored in
SLP mode, where the temperature sensor is always
powered by VBAT_RTC.
Reserved
28A0[7] 0 – R/W Must always be zero.
TEMP_TEST[1:0] 2500[1:0] 0
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.
– R/W _{TEMP_TEST Function}
00
Normal operation
01
Reserved for factory test
1X
Reserved for factory test
STEMP[10:3]
STEMP[2:0]
2881[7:0]
2882[7:5]
R The result of the temperature measurement.
R 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]
2885[7:0] –
– R The result of the battery measurement.
BCURR
2704[3]
0
0
R/W
Connects a 100 µA load to the battery (VBAT_RTC
pin).
2.5.6 71M6xx3 Temperature Sensor
The 71M6xx3 includes an on-chip temperature sensor for determining the temperature of its bandgap
reference. The primary use of the temperature data is to determine the magnitude of compensation
required to offset the thermal drift in the system for the compensation of the current measurement
performed by the71M6xx3. See the 71M6xxx Data Sheet for the equation to calculate temperature from the
71M6xx3 STEMP[10:0] reading. Also, see 4.5 Metrology Temperature Compensation on page 74.
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