ulp temperature compensated rtc on msp430f6736 design …

USCIA1

UART or SPIV1-/

Vref(O) USCIA0

Vref(I)

USCIA2

LF crystal

32kHz

XIN

XOUT

24-bit SD

Analog to

DigitalI In

V In

From utility

CT

V1+

I1+

I1-

I2+

I2-

N(L) L(N)

RST

VSS

VCC

Application interfaces

MSP430F6736

LOAD

V1-

VREF

PULSE1

PULSE2

USCIB0

UART or SPIUART or SPI

I C or SPI2

Sx,COMx

MAX

A

B

CkWhREACTEST kW

I/O

ADC10

100 K

NTC

TI DesignsULP Temperature Compensated RTC on MSP430F6736Design Guide

TI Designs Design FeaturesTI Designs provide the foundation that you need • On-Chip RTC_C Module and ADC10 for Ultra-Lowincluding methodology, testing and design files to Power and High-Accuracy RTC Calendarquickly evaluate and customize the system. TI Designs • Reduces Cost of E-Meter Applicationhelp you accelerate your time to market.

• High-Integration Chip a Solution to Single-ChipElectricity MetersDesign Resources

Featured ApplicationsTIDM-

Tool Folder Containing Design FilesTEMPCOMPENSATED- • Smart E-MeterRTC

• Single-Phase E-MeterMSP430F6736 Product Folder• Three-Phase E-MeterSN65HVD3082E Product Folder

UA78L05 Product Folder • High-Accuracy RTC

ASK Our E2E ExpertsWEBENCH® Calculator Tools

An IMPORTANT NOTICE at the end of this TI reference design addresses authorized use, intellectual property matters and otherimportant disclaimers and information.

All trademarks are the property of their respective owners.

1TIDU600–November 2014 ULP Temperature Compensated RTC on MSP430F6736 Design GuideSubmit Documentation Feedback

Copyright © 2014, Texas Instruments Incorporated

http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC



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http://www.ti.com/product/UA78L05

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http://e2e.ti.com/support/development_tools/webench_design_center/default.aspx

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http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=TIDU600

RTCDOW

Calendar

RTCMONRTCYEARLRTCYEARH RTCDAY

RTCTEV

00011011

minute changed

RTCBCD

Alarm

RTCAHOURRTCADAYRTCADOW RTCAMIN

Set_RTCTEVIFG

Set_RTCAIFG

2

EN

EN

EN

RT1PS

Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

Set_RT1PSIFG

EN3

RT1IP

RT0PS

Set_RT0PSIFG

EN

110101100011010001000

3

RT0IP

RTCHOLD

Keepout

Logic

Set_RTCRDYIFG

Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

111

hour changed

midnight

noon

RTCHOUR RTCMIN RTCSEC

110101100011010001000

111

from 32kHzCrystal Osc.

RTCOCALS RTCOCAL

ENCalibration

Logic

8

RTCTCMPS RTCTCMP

8

RTCHOLD

Key System Specifications www.ti.com

1 Key System SpecificationsThe RTC_C module in MSP430F673x functions as the real-time clock (RTC) in smart meters. RTC_Cfeatures include the following:• Real-time clock and calendar mode providing seconds, minutes, hours, day of week, day of month,

month, and year (including leap year correction)• Protection for real-time-clock registers• Interrupt capability• Selectable binary coded decimal (BCD) or binary format• Programmable alarms• Real-time clock calibration for crystal offset error• Real-time clock compensation for crystal temperature drifts• Operation in LPM3.5• Operation from a separate voltage supply with programmable charger

Figure 1. RTC_C Block Diagram

2 ULP Temperature Compensated RTC on MSP430F6736 Design Guide TIDU600–November 2014Submit Documentation Feedback


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UnifiedClock

System

128kB96KB64KB32KB16KB

FlashMCLK

ACLK

SMCLK

CPUXV2and

WorkingRegisters(25MHz)

EEM(S: 3+1)

XIN XOUT

JTAG/SBW

Interface/

Port PJ

eUSCI_A0eUSCI_A1eUSCI_A2

(UART,IrDA,SPI)

SD24_B

3 Channel2 Channel

ADC10_A

10 Bit200 KSPS

LCD_C

8MUXUp to 320Segments

REF

Reference1.5V, 2.0V,

2.5V

DVCC DVSS AVCC AVSS PA

I/O PortsP1/P2

2×8 I/OsInterrupt

& Wakeup

PA1×16 I/Os

P1.x P2.xRST/NMI

TA0

8kB4KB2KB1KB

RAM

PJ.x

DMA

3 Channel

PMMAuxiliarySupplies

LDOSVM/SVS

BOR

MPY32

SYS

Watchdog

PortMapping

Controller

CRC16

P9.x

PD

I/O PortsP7/P8

2×8 I/Os

PD1×16 I/Os

I/O PortsP9

1×4 I/O

PE1×4 I/O

P7.x P8.xPEPC

I/O PortsP5/P6

2×8 I/Os

PC1×16 I/Os

P5.x P6.x

PB

I/O PortsP3/P4

2×8 I/Os

PB1×16 I/Os

P3.x P4.x

eUSCI_B0

(SPI, I2C)

RTC_C

(32kHz)

AUX1 AUX2 AUX3

TA1TA2TA3

Timer_A2 CC

Registers

Timer_A3 CC

Registers

www.ti.com System Description

2 System DescriptionThis report introduces the methodology to implement an ultra-low-power real-time clock (RTC) withtemperature compensation functions in MSP430F6736. This report describes the crystal’s temperaturecharacteristics to use MSP430F6736’s RTC_C module plus software to implement an ultra-low-powerRTC, with an automatic temperature compensation feature and second ticks generation function. Thisreport finally builds up a reference code that runs in MSP430F6736 and provides test results.

2.1 MSP430F6736The MSP430F67xx series are microcontroller configurations with three high-performance 24-bit sigma-delta A/D converters, a 10-bit analog-to-digital (A/D) converter, four enhanced universal serialcommunication interfaces (three eUSCI_A and one eUSCI_B), four 16-bit timers, a hardware multiplier,direct memory access (DMA), a real-time clock module with alarm capabilities, an LCD driver withintegrated contrast control, an auxiliary supply system, and up to 72 I/O pins in 100-pin devices and 52 I/Opins in 80-pin devices.

Figure 2. MSP430F6736 Functional Block Diagram

2.2 SN65HVD3082ESN65HVD3082E is a group of half-duplex transceivers designed for RS-485 data-bus networks. Poweredby a 5-V supply, these transceivers are fully compliant with the TIA/EIA-485-A standard. With controlledtransition times, this device is suitable for transmitting data over long twisted-pair cables. This device isoptimized for signaling rates up to 200 kbps and is designed to operate with a very low supply current,typically 0.3 mA, exclusive of the load. In the inactive shutdown mode, the supply current drops to a fewnanoamps, making these devices ideal for power-sensitive applications.

2.3 UA78L05This series of fixed-voltage integrated-circuit voltage regulators is designed for a wide range ofapplications, including on-card regulation to eliminate noise and distribution problems associated withsingle-point regulation. In addition, the applications can be used with power-pass elements to make high-current voltage regulators. One of these regulators can deliver up to 100 mA of output current. Theinternal limiting and thermal shutdown features of these regulators make them essentially immune tooverload. When used as a replacement for a Zener diode-resistor combination, output impedance caneffectively improve with a lower-bias current.



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USCIA1

UART or SPIV1-/

Vref(O) USCIA0

Vref(I)

USCIA2

LF crystal

32kHz

XIN

XOUT

24-bit SD

Analog to

DigitalI In

V In

From utility

CT

V1+

I1+

I1-

I2+

I2-

N(L) L(N)

RST

VSS

VCC

Application interfaces

MSP430F6736

LOAD

V1-

VREF

PULSE1

PULSE2

USCIB0

UART or SPIUART or SPI

I C or SPI2

Sx,COMx

MAX

A

B

CkWhREACTEST kW

I/O

ADC10

100 K

NTC

Block Diagram www.ti.com

3 Block Diagram

Figure 3. Block diagram for E-Meter RTC application using MSP430F6736

4 System Design TheoryThe real-time clock (RTC) is the fundamental function for multi-toll controls in the smart meter. The RTCgenerates two outputs for the other functions of the smart meter:1. The calendar—The calendar uses the format of year/month/day/hour/minute/second. The calendar

must be non-volatile during power down and reset because the smart meter may work in very toughenvironments, but the electric energy bill must never be wrong.

2. The 1-second pulse—The 1-second pulse is a square pulse signal generated by the RTC chip onceper second. This pulse is used for RTC calibration and certification.

Both the calendar and 1-second pulse are related to the multi-toll control, thus they have very strictrequirements:1. Accuracy—The RTC must be very accurate. In most specifications, the error rate under room

temperature should be fewer than 5 ppm.2. Temperature compensated—The crystal’s frequency may drift away when working temperatures rise or

drop. The RTC must be able to compensate for the crystal's drift to remain accurate across the wholeworking range. The RTC error rate across the whole working temperature has different specifications indifferent countries. For example, in China, the limitation is 10 ppm.

3. Ultra-low power—The power consumption of the RTC is very critical. The RTC functions must beawake even during power failure. During power failure, the smart meter is powered by an embeddedunchangeable battery that must be run for at least five years. In most countries, the powerconsumption of the RTC must be lower than 2 µA.



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E = K (T - T0) (T - T0) + B´ ´

-160.0 PPM

-140.0 PPM

-120.0 PPM

-100.0 PPM

-80.0 PPM

-60.0 PPM

-40.0 PPM

-20.0 PPM

0.0 PPM

-40°C -20 C° 0 C° 20°C 40 C° 60 C° 80°C

Temperature

DF

/F

T0 = 25°C ±5°C

–0.035 ppm/°C × (T – T0) ±10%2 2

www.ti.com System Design Theory

4.1 Crystal Frequency Temperature CompensationAll MCU-based smart-meter solutions use a 32-kHz low-frequency watch crystal as one of the clock'ssources. The frequency output of the crystal varies considerably due to the drift in temperature. The RTCmust compensate for this temperature drift for higher accuracy in time keeping from standard crystals. Thetypical temperature curve of a 32-KHz crystal is shown in Figure 4:

Figure 4. Crystal Temperature Curve

The above curve is very close to a parabola curve, so the frequency variation of a 32-KHz crystal can bepredicted by the following formula:

(1)

Here, E is the frequency error of the crystal (which relates to three factors: K, T0, and B). T is the crystal'sworking temperature.

B is the frequency deviation of a crystal in room temperature. Each crystal’s frequency deviation is not thesame, but each crystal’s frequency deviation is its inherent characteristic and will not change with time.The crystal’s deviation can be measured at room temperature (around 25°C) because the parabola curveis quite flat at the central point.

T0 and K are two factors to describe the parabola curve, denote the curve’s central point, and roll downspeed, respectively. These two factors are decided by the production process of the crystal. Usually, T0and K are almost the same among the same batch of crystals.

In some circumstances, the whole crystal's temperature curve will be divided into three or five segmentswithin the temperature axis. On each of the segments is a parabola curve to represent the temperaturefeature of the crystal in this temperature range. The three or five parabola curves compose the wholepicture of a crystal’s temperature feature, making it possible to better approach the crystal’s realcharacteristics.

Normally, the 32-KHz crystal vendors can provide such temperature curves of their crystals and therelated parameters K and T0 to their end users. This process makes it possible to compensate crystalfrequency error with software, without much effort on calibration.



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TEMP 2NTC

TEMP1 1 2 TEMP 2

V R RR

V (R R ) V R

´ ´

=

´ + - ´

TEMPNTC

V RTC TEMP

V RR

V V-

´

=

-

100 K

NTC

R

TEMP

V-RTC

TEMP1

R1

1M

R2

1M

100 K

NTC

R

TEMP

V-RTC

A. Simplest Structure B. VCC Drift-Considered Structure

System Design Theory www.ti.com

4.2 Temperature MeasurementAfter getting the crystal temperature factors K and T0 from the crystal vendor and calibrating the crystal’sdeviation in room temperature, measure the working temperature for an overall frequency-errorcalculation.

MSP430F6736 integrated a 10-bit ADC, to which an on-chip temperature sensor is connected internally.Because the MSP430F6736 IC is very closed to 32-KHz crystal on an e-meter board, the temperature ofthe crystal can be treated identically to the one measured by the on-chip temperature sensor. Composingan on-chip ADC10 and an on-chip temperature sensor is the simplest way to measure the crystal'sworking temperature.

To use internal temperature sensor for temperature measurement, set the ADC10 on channel 10 andguarantee the sample period is greater than 30 µs.

One important limitation of MSP430F6736’s internal temperature sensor is accuracy: its maximum error is3°C, which results in up to a 13-ppm error on frequency calculations in an 85°C testing point. TheMSP430F6736's internal temperature sensor is hard to be used in e-meter applications before beingmanually calibrated.

For better accuracy, use the external temperature sensor. A typical low-cost temperature sensor is theNTC resistor. The NTC resistor’s resistance changes dramatically when it’s working temperature changes.If we can measure the resistance of NTC, we can get its working temperature. Figure 5 shows the circuitto measure NTC resistance.

Figure 5. NTC Temperature Measurement Circuit

The simplest usage of NTC is as part A of Figure 5 shows. The V-RTC is the power source for the resistorladder. This power source is supplied by MSP430F6736 GPIO and can be shut down to GND for powersaving when temperature is not measured. TEMP is the tap where the voltage on NTC is fed out toADC10. The resistor of NTC will be as follows:

(2)

V-RTC is the power supply voltage for MCU. R is the resistance for R. If we can measure the voltage dropon NTC (VTEMP) with ADC10, we can calculate the resistance of NTC.

In real e-meter applications, the power supply for the MCU V-RTC may drift because of workingtemperature or disturbance from a power grid. The calculated resistance of NTC may have errors, so weprefer to use the second structure to measure as part B of Figure 5 shows.

In this structure, a new branch resistor ladder is implemented, so the calculation on NTC resistance will beas follows:

(3)

The NTC resistance calculation of structure B is irrelevant to power supply.



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Foreground TA0 ISR

RTC_C init

AD10 ISR

Set Pin V-RTC to 1

RTCTCRDY flag set?

RTC_C start

Unlock RTC_C

Set RTCOCAL

lock RTC_C

Setup TA0

Start ADC10

Start TA0

Get Vtemp1

Get Vtemp

Calculate temperature

Set Pin V-RTC to 0

Calculate Frequency

error in PPM

Set RTCCMP

Clear ADC10IFG0


4.3 The Implementation of RTC_C ModuleThe RTC_C module allows users to compensate crystal errors that either result from crystal individualfrequency offset or temperature influence. For crystal frequency offset, users must calibrate the crystal inroom temperature and get the error between the crystal frequency and standard 32768 Hz. Fortemperature influence, users can calculate the crystal frequency error based on the crystal’s temperaturecurve with the measured temperature. All errors are in PPM and need to be written into RTCOCAL andRTCTCMP respectively to compensate offset and temperature influence.

The RTC_C module has a dedicated clock source from the external 32-KHz crystal and has a dedicatedpower supply. The RTC_C module can work in stand-alone mode without taking any MCU MIPS, and thepower consumption is typically only 0.34 µA in room temperature.

The RTC_C module also integrates calendar and alarm functions.

Figure 6 shows the RTC_C module implementation flow chart.

Figure 6. RTC_C Module Software Control Flow

The RTC_C module can also output second ticks (1-Hz clock) on the RTCCLK pin. However, because thefrequency compensation in RTC_C module is in 60 µs per step, the second ticks output from the RTC_Cmodule can only be accurate in a one-minute scale. For example, the accumulated error of 60 consecutivesecond ticks can be calibrated to 0, but the error of a single second tick will be up to 60 ppm.



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Crystal Offset

Crystal

Temperature

Coefficient+

1MHz SMCLK

TACCR

TAR

Basic count per

second

Timer_ASecond ticks


4.4 Ultra-Low-Power Second Ticks GenerationIn many applications, the error on second ticks must be measured solely or in 10-second scales. Here, weuse software to fine tune the accuracy of every second tick.

MSP430F6736 has a very flexible clock system, and the integrated FLL plus many pre-scale dividerseasily facilitate a 1-MHz SMCLK clock internally. Because the SMCLK is actually sourced from theexternal 32-KHz crystal through PLL, the error rate of the external crystal is the same as that of SMCLK.The frequency compensation to SMCLK can also be made with the same rate as the crystal.

Figure 7 shows how to use the 1-MHz clock and Timer_A to compensate frequency errors and generatesecond ticks.

Figure 7. Frequency Compensation and Second Ticks Generation

In the frequency compensation stage, use the same process as with RTC_C:1. Get working temperature through external NTC2. Calculate the overall frequency error E caused by temperature and initial deviation based on crystal’s

temperature parabola curve Equation 1, in PPM3. Subtract the frequency error E and get the exact SMCLK clock count per second.

Through Timer_A, the second ticks generation is actually a frequency divider. Because the clock source ofTimer_A is the 1-MHz SMCLK, adding or subtracting 1 SMCLK in TACCR is equal to fine tuning theoutput of the second ticks frequency by 1 ppm.

The limitation of the above temperature-compensated second tick generation system is the powerconsumption. If the 1-MHz SMCLK keeps running for Timer_A, MSP430 has to run in LPM0 whilesleeping, and the power consumption is typically 83 µA. However, in many applications (like e-meter), thewhole system is powered by batteries if the main power source drops. The system requires RTC’s powerconsumption to reduce to micro-ampere level.

Because high-speed clocks consume more power during the same time, one way to cut down powerconsumption is to compose different clocks—high speed clock and low speed clock—to fill the whole 1-second counting period.



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TA0

0FFFFh

TA0CCR0

TA0CCR1

TA2

0FFFFh

TA2CCR0

TA2CCR1

capture Tick 1s pulse and

switch off FLL

Switch on FLL

and TA2

Frequency

Compensation

Sourced from

32KHz ACLK

Sourced from

1MHz SMCLK

E LPM3 LPM0

32668 100I I I

32768 32768= +

1M

CLK

...32K

CLK

1 Second

...

32668/32768 second

Switch to High

Frequency clock Generate 1s pulse


Figure 8. Fill 1-Second Counting Period with Different Clocks for ULPP

As Figure 8 shows, if we use a 32-KHz clock to count for 32766 / 32768 second and use another 1-MHzclock to count the last 100 / 32768 second and decide on the point when we generate second ticks, wecan still fine tune the second tick's accuracy in 1-ppm steps while reducing the overall power consumption

dramatically to the following:

Where IE is the average power consumption, ILPM0 is the power consumption in LPM0 mode, and ILPM3 isthe power consumption in LPM3 mode. In the MSP430F6736 data sheet, the power consumption forLPM0 mode is 83 µA, and the power consumption for LPM3 mode is 2.5 µA. The average powerconsumption for software RTC and second ticks generation is 2.74 µA.

In this application, two Timer_A modules are used to implement clock switching and second ticksgeneration. Figure 9 shows the time sequence of two TA modules.

Figure 9. Ultra-Low-Power Second Ticks Generation



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TA0

CCR1 ISR CCR0 ISR

Foreground

Setup TA0:

32kHz Clock

Up counting

Compare mode

Switch on FLLSetup TA2:

1MHz Clock

Continue counting

Capture mode

CCR1 event? CCR0 event?

Calculate frequency

error

Set TA2 to compare out

mode for second tick

Update TA0CCR2 with

TA2CCR1, TA0R and

frequency error

TA2

CCR1 HW Auto

capture

CCR0 ISR

Capture TA0R to

TA2CCR1

CCR0 event?

End second tick

Switch off TA2Switch on TA2

Switch off FLL


TA2 sources from the 1-MHz SMCLK. TA2 is shut down until TA0 ISR wakes it up. TA0 sources from the32-KHz ACLK. TA0 is always on, and it runs in up and compare-out modes. TACCR0 stores the valuewhen TA2 is switched on to fine tune the second ticks. Because TA2 sources from SMCLK, switch on FLLfor several ACLK before switching on TA2, so that enough time exists to stabilize SMCLK before TA2 isused for SMCLK counting. TACCR1 stores the value when FLL will be switched on.

The TA0 and TA2 running sequence will be as follows:1. At the beginning, TA0 is on and MCU runs in LPM3 mode.2. When TA0R reaches TA0CCR1, FLL is switched on (MCU switches to LPM0) and TA2 is started in

TA0 ISR. TA2 is initiated in capture mode and TA2CCR1 is set to always capture on ACLK.3. Several ACLK later when TA0CCR1 is reached and TA0 ISR is triggered, frequency errors accumulate

caused by temperature change and offset deviation. These accumulations are used to calculate whento send out second ticks by summing frequency error with TA2CCR1. Finally, the summary toTA2CCR0 is written, and TA2 is set to compare-out mode to generate second ticks.

4. In the last step after generating second ticks, switch off TA2 and FLL and go back to LPM3 in TA2ISR.

NOTE: We used TA2 in capture mode and recorded the exact TA2R value to TA2CCR1 instead ofdirectly reading the TA2R value. By doing this, we can avoid the error caused by TA2 ISRinterrupting the latency difference.

Figure 10 is the software flow chart for ULPP second ticks generation.

Figure 10. ULP Second Tick Software Flow



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www.ti.com Getting Started Hardware

5 Getting Started HardwareTo debug the system, the necessary test points are designed on J16 as shown in Figure 11. The testingwire must connect to these points to connect with the debugging tools. To test the frequency errors, usethe frequency equipment that has 1-ppm accuracy, and connect the wire from J6 to the frequencyequipment. To test the influence by temperature, use a thermostat that can adjust the temperature from–40 to 80.

Figure 11. MSP430 Spy-Bi-Wire Interface and Second Pulse interface

5.1 MSP430 USB Debugging InterfaceThe MSP430-FET430UIF, which is shown in Figure 12, debugs the firmware on the MCU.

Figure 12. MSP430-FET430UIF



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1

3

5

7

9

11

13

2

4

6

8

10

12

14

TEST/SBWTCK

MSP430Fxxx

RST/NMI/SBWTDIOTDO/TDI

TCK

GND

TEST/VPP

JTAG

VCC TOOL

VCC TARGET

330Ω

R2

J1 (see Note A)

J2 (see Note A)

Important to connect

V /AV /DVCCCC CC

V /AV /DVSS SS SS

R147 kΩ

C12.2 nF

VCC

C210 µF

C30.1 µF

A If a local target power supply is used, make connection J1. If power from the debug or programming adapter is used,

make connection J2.

Getting Started Firmware www.ti.com

To debug the MCU software, connect only four points on the board to the debugger: VCC, GND, RST,and TEST. The connection should follow Figure 13.

Figure 13. Spy-Bi-Wire Connection

6 Getting Started FirmwareThis firmware mainly includes the folder ”emeter-rtc”, which includes emeter-rtc-inter.c, emeter-rtc.c,emeter-rtc-lib.c, and more. For convenience in further development, the firmware provides the APIsthat realize functions of the RTC calibration and RTC parameters' reading. This firmware will occupysome hardware resources as shown in Table 1:

Table 1. Resources Used by Firmware

RESOURCE RTC FIRMWAREFLASH 3220 bytesRAM 78 bytesTA0 YTA1 Y

ADC10 YSMCLK Require 4 MHz

I/O TA1.0 PWM second-pulse outputREF ADC using REF 2.5 V

If we need to use this firmware, we only need include the “emeter-rtc-inter.h” file and add the “emeter-rtc\emeter-rtc-6736\Debug\Exe\emeter-rtc-6736.r43” file to the project.



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www.ti.com Getting Started Firmware

6.1 Firmware API

This firmware provides two API: one is for getting, and the other is for setting.

The following function sets all parameters that will be used by the firmware:

void set_rtc_parameter(int address, int32_t value)

The following function gets all parameters from the firmware inside:

int32_t get_rtc_parameter(int address, void *ptr)

Below are the parameters to get or set.• RTC_CRYSTAL_BASE_OFFSET

Description: The fixed bias of the oscillator at room temperature. Reads and writes.Unit: ppm.Note: ppm > 0 means faster than the standard, and ppm < 0 means slower than the standard.

• RTC_CURRENT_TIMEDescription: Gets and sets current time. Reads and writes. The time is structured as follows:struct rtc_interface

uint8_t year; value: 0–100uint8_t month; value: 1–12uint8_t week; value: 0–6, Sunday = 0uint8_t day; value: 1–28, 30, 31uint8_t hour; value: 0–23uint8_t minute; value: 0–59uint8_t second; value: 0–59

;Note: The void is called set_rtc_parameter(int address, int32_t value) or int32_t get_rtc_parameter(intaddress, void *ptr) for RTC_CURRENT_TIME, which needs to pass the point of the struct rtc_interfacevariable.

• RTC_CURRENT_MODEDescription: RTC current working mode. Reads and writes.Value: Includes two modes:enum RTC_STATUS RTC_LOW_POWER_STATUS = 0, low-power mode RTC_OPEN_STATUS, normal power mode;Note: In low-power mode, this firmware will not output a second pulse; it will only compensate for theerror influenced by the temperature.

• RTC_CURRENT_TEMPDescription: Gets current temperature. Only reads.Unit: 0.25°C

• RTC_ERROR_STATUSDescription: Reports if RTC has something wrong. Only reads.Value: 1 = error, 0 = normal

• RTC_ADC_BATTERY_RAWDescription: Gets battery ADC value using 2.5-V REF. Only reads.



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Getting Started Firmware www.ti.com

Value: 1 = error, 0 = normal

• RTC_NTC_POWER_ON_CBDescription: Callback function that lets the power I/O pin high.

• RTC_NTC_POWER_OFF_CBDescription: Callback function that lets the power I/O pin low. Only writes.

• RTC_CRYSTAL_COEFF0• RTC_CRYSTAL_COEFF1• RTC_CRYSTAL_COEFF2• RTC_CRYSTAL_COEFF3• RTC_CRYSTAL_COEFF4• RTC_CRYSTAL_COEFF5

Description: Sets crystal curve coefficient according to the crystal curve parameter.



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www.ti.com Getting Started Firmware

6.2 Firmware Use in IAR Project

Figure 14. IAR Project File: E-Meter-RTC-6736 Figure 15. IAR Project File: E-Meter-APP-6736



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Test Data www.ti.com

7 Test Data

Table 2. Test Data When Using Temperature Compensated

NOIDEAFREQ ERR GAP FREQ IDEAL FREQ MEAS FREQ CALIBRATIONIDEAL TEMP °C CALIBRATION(ppm) (ppm) (mHZ) (mHz) ERRERR73 83.75 91.7 1000 999.9083 –7.95 –6.9563 53.6 58 1000 999.942 –4.4 –3.453 30.15 32.7 1000 999.9673 –2.55 –1.5543 13.4 14.7 1000 999.9853 –1.3 –0.333 3.35 4 1000 999.996 –0.65 0.3523 0 1 1000 999.999 –1 013 3.35 6 1000 999.994 –2.65 –1.653 13.4 17.7 1000 999.9823 –4.3 –3.3–7 30.15 34.7 1000 999.9653 –4.55 –3.55

–17 53.6 58 1000 999.942 –4.4 –3.4–27 83.75 88.3 1000 999.9117 –4.55 –3.55–37 120.6 123.3 1000 999.8767 –2.7 –1.7



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BL

CE

N

BE

EP

X2X1

SC

LS

DA

RB

RA

PL

C_

SE

T

PL

C_

RS

T

PL

C_

EV

PL

C_

ST

PL

CT

X

PL

C_

RX

P1O

UT

VR

TC

SH

OR

T

TX

_P

WM

CA

SE

SAMIO

ES

M_

VC

C

RX

_4

85

_1

TX

_4

85

_1

LED2

MOUTPUT

A_BAT

LE

D3

G132.768

X1

X2

C510.1U

R7247K

C482.2N

VDD

RST

C500.1U

VDD

R7410k

S9C52

0.1U

SHORT

SD0P01

SD0N02

SD1P03

SD1N04

SD2P05

SD2N06

VREF7

AV SS8

AV CC9

VA SYS10

NC11

NC12

NC13

P1.0/PM_TA0.0/VREF-/A214

P1.1/PM_TA0.1/VREF+/A115

P1.2/PM_UCA0RXD/PM_UCA0SOMI/A016

P1.3/PM_UCA0TXD/PM_UCA0SIMO/R0317

AUXVCC218

AUXVCC119

VDSYS20

DVCC21

DVSS22

VCORE23

XIN24

XOUT25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48 49

50

P3.2/PM_TACLK/PM_RTCCLK51

P3.3/PM_TA0.252

P3.4/PM_SDCLK/S3953

P3.5/PM_SD0DIO/S3854



P4.0/S3557

P4.1/S3458

P4.2/S3359

P4.3/S3260

P4.4/S3161

P4.5/S3062

P4.6/S2963

P4.7/S2864

P5.0/S2765

P5.1/S2666

P5.2/S2567

P5.3/S2468

P5.4/S2369

P5.5/S2270

P5.6/S2171

P5.7/S2072

P6.0/S1973

DVSYS74

DVSS75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

10

0

U26MSP430F67XX

SEG0SEG1SEG2SEG3SEG4SEG5SEG6SEG7SEG8SEG9SEG10SEG11SEG12SEG13SEG14SEG15SEG16SEG17SEG18SEG19SEG20

CO

M1

CO

M2

CO

M3

CO

M4

I1+I1-I2+I2-

V1+V1-

GNDVDSYS

INTRA

1234

J16

CON4

VDDGNDRSTTEST

VDDVDSYSVDDALERT_M

VREF

AVDDGND

GND

C530.47U

VCORE

C544.7U

VA SYS

RX

A

C5510U

LCDCAP

LC

DC

AP

C5610U

VD

D

C5710U

R73 10AVDDVDDC49

15PC47

15P

RT

VDSYS

VCORE

VREF

VA SYS

VDDVDD

AU

XV

CC

3

P1

.4/P

M_

UC

A1

RX

D/P

M_

UC

A1

SO

MI/

LC

DR

EF

/R1

3P

1.5

/PM

_U

CA

1T

XD

/PM

_U

CA

1S

IMO

/R2

3L

CD

CA

P/R

33

P8

.4/T

A1

.0P

8.5

/TA

1.1

CO

M0

CO

M1

CO

M2

CO

M3

P1

.6/P

M_

UC

A0

CL

K/C

OM

4P

1.7

/PM

_U

CB

0C

LK

/CO

M5

P2

.0/P

M_

UC

B0

SO

MI/

PM

_U

CB

0S

CL

/CO

M6

P2

.1/P

M_

UC

B0

SIM

O/P

M_

UC

B0

SD

A/C

OM

7P

8.6

/TA

2.0

P8

.7/T

A2

.1P

9.0

/TA

CL

K/R

TC

CL

KP

2.2

/PM

_U

CA

2R

XD

/PM

_U

CA

2S

OM

IP

2.3

/PM

_U

CA

2T

XD

/PM

_U

CA

2S

IMO

P2

.4/P

M_

UC

A1

CL

K

P2

.5/P

M_

UC

A2

CL

KP

2.6

/PM

_T

A1

.0P

2.7

/PM

_T

A1

.1P

3.0

/PM

_T

A2

.0

P3

.1/P

M_

TA

2.1

RS

T/N

M1

/SB

WT

DIO

PJ.

3/A

CL

K/T

CK

PJ.

2/A

DC

10

CL

K/T

MS

PJ.

1/M

CL

K/T

DI/

TC

LK

PJ.

0/S

MC

LK

/TD

O

TE

ST

/SB

WT

CK

P8

.3/S

0P

8.2

/S1

P8

.1/S

2P

8.0

/S3

P7

.7/S

4P

7.6

/S5

P7

.5/S

6

P7

.4/S

7P

7.3

/S8

P7

.2/S

9

P7

.1/S

10

P7

.0/S

11

P6

.7/S

12

P6

.6/S

13

P6

.5/S

14

P6

.4/S

15

P6

.3/S

16

P6

.2/S

17

P6

.1/S

18

RS

T

CD

RS

T

S-A

SA

MR

ST

SA

MC

LK

TE

ST

UP

PR

OG

IR C

LE

D4

SE

G3

2

SE

G3

1S

EG

30

SE

G2

9S

EG

28

SE

G2

7

SE

G2

6S

EG

25

SE

G2

4S

EG

23

SE

G2

2

SE

G2

1

www.ti.com Design Files

8 Design Files

8.1 SchematicsTo download the schematics for each board, see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.



http://www.ti.com




K1AN6*6*5

UP

R201100k

PROG

R202100k

K2AN6*6*5

C171

0.1UC1720.1U

R206

1K

R207

1KR203 1M

VDD

C1730.1U

123 4

56

K3KF-508

CASE

GND1

Vpp2

I/O3

RFU4

RFU5

CLK6

RST7

VCC8

U131

ESAM2605

SAMIO

SAMRST

SAMCLK

C321

0.1U

ESM_VCC

C32222P

R413 100

GND

GND

R414

4.7K

Q1263906

VDD

R412 1KR4114.7K

E _ V CC E_VCC

VDD VDD

Design Files www.ti.com



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TX_485_1

485_TX_1

485_GND

VDD

R124.7K

485_VCC

R141K

RX_485_1

485_RX_1GND

VDD

R133K

485_VCC

GN

D5

VC

C8

RD1

RE2

TE3

TD4

A6

B7

U53082

C60.1U

485_VCC

485_RX_1

485_DE_1

485_TX_1

R1733K

R18 33K

485_GND

485_GND

TV1PK6.8E

A

B

R11 470

1

2 3

4

U22501

1

23

4U3

2501

RT3

MZ27-51

R15

10K

Q103906

R16 2K

485_VCC

485_GND

485_TX_1

485_DE_1

12

J3

CON6

P+P-

S+S-

AB

R25

4.7K

Q83904

GND

R24

100

VDDD5AT205B

TX_PWM

12

J5 CON2

12

J6

R292K

R303K

PLC_RX1

PLC_RX

R33

4.7K Q39013

Q49013

R3410K

R3510K

PLC_TX1

PLC_TX

VCC

R36 4.7KPLC_EV Q5

3904

R3710K

VCC

PLC_EV1

R312K

R323K

PLC_ST1

PLC_ST

GNDRXA

C7

0.1uRX

1GND

2VCC

3

U6HM238

VDD

IR_C Q93906

R26 4.7k

R38 4.7KPLC_SET Q6

3904

R3910K

VCC

PLC_SET1

R40 4.7KPLC_RST Q7

3904

R4110K

VCC

PLC_RST1

PLC_RST1

PLC_SET1

PLC_RX1

PLC_TX1

VCC

GND

+12V

PLC_ST1

123456789101112

J4

FD2*6

PLC_RESPLC_EV1




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BEEP1

//SMB1275P2305AR1

//4.7K

R2 //100

Q1

//3904

VDD

BEEP

A01

A12

A23

VSS4

SDA5

SCL6

WP7

VCC8

U41 24LC256

C131

0.1U

VDDSDA

SCL

GND

R151

7.5K

R152

7.5K

C132

180P C133

180P

1

2 3

4

U51

PS2501R171

1k

GND

P+

P-

P1OUT

C1510.1u

1

2 3

4

U52

PS2501R174

1k

GND

C1520.1u

MULTI

Q37

3906

INTRA VDD

MULTI

MOUTPUT R177

4.7K

Q36

3904

S+

S-

C153

1000P

C154

1000P

GNDLED2R343

1k

CO

M1

CO

M2

CO

M3

CO

M4

SE

G0

SE

G1

SE

G2

SE

G3

SE

G4

SE

G5

SE

G6

SE

G7

SE

G8

SE

G9

SE

G1

0

SE

G11

SE

G1

2

SE

G1

3

SE

G1

4

SE

G1

5

SE

G1

6

SE

G1

7

SE

G1

8

D113L3WR-C

SE

G1

9

SE

G2

0

SE

G2

1

SE

G2

2

SE

G2

3S

EG

24

SE

G2

5S

EG

26

SE

G2

7S

EG

28

SE

G2

9

SE

G3

0

SE

G3

1

R342

4.7K

Q111

3904

VDD1

BLCEN

R341

300

GND

LED3

D114L3WR-C

LED4

D115L3WR-C

SE

G2

B1

SE

G

2A

2

SE

G

3B

3

SE

G

3A

4

SE

G4

B5

SE

G4

A6

SE

G7

SE

G8

SE

G1

B9

SE

G1

A1

0

SE

G11

SE

G1

2

SE

G1

3

SE

G1

4

SE

G1

5

CO

M1

16

CO

M2

17

CO

M3

18

CO

M4

19

SE

G2

0S

EG

9A

21

SE

G9

B2

2S

EG

8A

23

SE

G8

B2

4S

EG

7A

25

SE

G7

B2

6S

EG

6A

27

SE

G6

B2

8S

EG

29

SE

G3

0S

EG

31

SE

G5

A3

2S

EG

5B

33

SE

G3

4S

EG

35

SE

G3

6

0

LCD1

LCD-JY09484A

SE

G3

2

A K

D111

C01W-7131-6

R346

1K

R347

1K

C281

68P

C282

68P

C283

68P

C284

68PC285

68P

C286

68P

C287

68P

C288

68P

C289

68P

C290

68P

C291

68P

C292

68P

C293

68P

C294

68P

C295

68PC296

68P

C297

68P

C298

68P

C299

68P

C300

68P

SEG0

SEG1

SEG2

SEG3

SEG4

SEG5

SEG6

SEG7

SEG8

SEG9

SEG10

SEG11

SEG12

SEG13

SEG14

SEG15

COM1

COM2

COM3

COM4

C301

68P

C302

68P

C303

68P

C304

68PC305

68P

C306

68P

C307

68P

C308

68P

C309

68P

C310

68P

C311

68P

SEG16

SEG17

SEG18

SEG19

SEG20

SEG21

SEG22

SEG23

SEG24

SEG25

SEG26

C312

68P

C313

68P

C314

68P

SEG27

SEG28

SEG29

R345300




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T-220N

R91240K-1%

R92150K-1%

R93150K-1%

R941K-1%

C7747p

R95

100-1%C7647p

R96

1K-1%

R97//10-1%

R98 1K-1%

C7947P

I1+1

P13

1

P14R99

1K-1%

C8047P

I1-

GND

B!

A!

R10010-1%

R1011K-1%

C8247P

I2+1

P15

1

P16R102

1K-1%

C8347P

I2-

GND

V1+

V1-

Z6

STBL-120

Z7

STBL-120

Z8

STBL-120

Z9

STBL-120

C7815NF

C8115NF

C8415NF

S16S

GND

S17S

GND

RELAY+ RELAY-

12

J46

CON2

R211

5.1K

R2125.1K

Q519013

R2131K

Q539013

Q529012

R215

1K

R2145.1K

Q549012

Q559013

R216

1K

R2175.1K

Q569013

R2181K

+12V

R2195.1K

R220

5.1K

RA RB

TV33P6KE30CA

RELAY+RELAY-

R24120K

R242RT

VRTC

RT R261

300K

R262

300K

R263

300K

R264

300K

1

2 3

4U79

PS-2501

D81M7

T-220N

1P39

R2651M

C2010.1U

VDD

S-A

R2811M

R2821M

BAT+

C2111000P

A_BATR283 0R




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12345678

J66LL

NN

+

C229

470U/16V

+

C221100U/35V

1P46

N

1P47

L

Z24

B62

RV3120K681

Z25

B62

T-220N

L

N

V2MB6S

+

C225470U/35V

+

C226 C2270.1U

C228

0.1U

VCC+12V

BAT3CR1/2AA

S40BAT+ VDD

+5V2

GN

D3

Vin1

U8878L05

C2220.1U

C2230.1U

+C224220U/16V

485_GND

485_VCC

D92

LL4148

1

3

+2

6

7

+

4

5

+T1

JS28D20-18A

D91M7

485_VCC_12

+

C233470UF/35V

D94LL4148

VIN3

GN

D2

VOUT1

U89 HT7550

D95LL4148

PT7MZ4

R29810K

R3005.1K

C2321000P

ALERT_M

ZD23

1N4744A

D961N4148

VCCVCC

VDD

VDD1


8.2 Bill of MaterialsTo download the bill of materials (BOM), see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.

Table 3. BOM

DESCRIPTION VALUE DESIGNATOR PCS/UNIT FOOTPRINT MANUFACTURERC6, C7, C50, C51,C52, C131, C151,

SMD, Capacitor, C152, C171, C172,0.1 µF 17 603 Yageo±20% C173, C201, C222,C223, C227, C228,C321

SMD, Capacitor, 0.47 µF C53 1 603 Yageo±20%SMD, Capacitor, 2.2 nF C48 1 603 Yageo±20%SMD, Capacitor, 4.7 µF C54 1 603 Yageo±20%SMD, Capacitor, 10 µF C55, C56, C57 3 805 Yageo±20%SMD, Capacitor, C153, C154, C211,1000 pF 4 603 Yageo±20% C232SMD, Capacitor, 180 pF C132, C133 2 603 Yageo±10%SMD, Capacitor, 15 nF C78, C81, C84 3 603 Yageo±10%SMD, Capacitor, 15 pF C47, C49 2 603 Yageo±10%



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Table 3. BOM (continued)DESCRIPTION VALUE DESIGNATOR PCS/UNIT FOOTPRINT MANUFACTURER

SMD, Capacitor, 22 pF C322 1 603 Yageo±10%SMD, Capacitor, C76, C77, C79,47 pF 6 603 Yageo±10% C80, C82, C83SMD, Capacitor, 68 pF C281-C314 34 603 Yageo±10%SMD, Resistor, ±5% O Ω R283 1 603 Yageo

R15, R34, R35,SMD, Resistor, ±5% 10 k R37, R39, R41, 8 603 Yageo

R74, R298R94, R96, R98,SMD, Resistor, ±1% 1 k 6 603 YageoR99, R101, R102R14, R171, R174,R206, R207, R213,

SMD, Resistor, ±5% 1 k R215, R216, R218, 13 603 YageoR343, R346, R347,R412

SMD, Resistor, ±5% 2 k R16, R29, R31 3 603 YageoSMD, Resistor, ±5% 20 k R241 1 603 YageoSMD, Resistor, ±5% 3 k R13, R30, R32 3 603 YageoSMD, Resistor, ±5% 33 k R17, R18 2 603 YageoSMD, Resistor, ±5% 300 R341, R345 2 603 YageoSMD, Resistor, ±5% 100 k R201, R202 2 603 YageoSMD, Resistor, ±1% 100 R95 1 603 YageoSMD, Resistor, ±5% 100 R24, R413 2 603 YageoSMD, Resistor, ±1% 470 R11 1 603 Yageo

R12, R25, R26,R33, R36, R38,SMD, Resistor, ±5% 4.7 k 11 603 YageoR40, R177, R342,R411, R414

SMD, Resistor, ±5% 47 k R72 1 603 YageoR211, R212, R214,

SMD, Resistor, ±5% 5.1 k R217, R219, R220, 7 603 YageoR300

SMD, Resistor, ±1% 10 R100 1 603 YageoSMD, Resistor, ±5% 10 R73 1 603 YageoSMD, Resistor, ±5% 7.5 k R151, R152 2 603 Yageo

R203, R265, R281,SMD, Resistor, ±5% 1 M 4 603 YageoR282R261, R262, R263,SMD, Resistor, ±5% 300 k 4 805 YageoR264

SMD, Resistor, ±1% 150 k R92, R93 2 1206 YageoSMD, Resistor, ±1% 240 k R91 1 1206 YageoSMD, Diode IN4148 D92, D94, D95, D96 4 IN4148-SMTSMD, MCU MSP430F6736 U26 1 TQFP100-0.26 Texas InstrumentsSMD, RS485 SN65HVD3082E U5 1 SOIC8 Texas InstrumentsSMD, EEPROM 24LC256B-I/SN U41 1 SOIC8

Q3, Q4, Q5, Q6,SMD, Q7, Q8, Q36, Q51, NXP MMBT39043904 12 3904_3906Transistors,NPN Q53, Q55, Q56, MMBT3906

Q111,SMD, Q9, Q10, Q37, Q52, NXP MMBT39043906 6 3904_3906Transistors,PNP Q54, Q126 MMBT3906SMD, LDO 78L05 U88 1 SOT-89 Texas Instruments



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SMD, LDO HT7550 U89 1 SOT-89 HTSMD, Rectifier M7 D81, D91 2 IN5817-SMT ChangjiangDiodeSMD, Rectifier MB6S V2 1 MBS-1 ChangjiangBridgeSMD, NTC RT-10 k R242 1 805 ExsenseSMD, Bead STBL-120 Z6, Z7, Z8, Z9 4 805 YageoThrough-hole, LED RED LED-Ф5 D113, D114, D115 3 LED ChangjiangThrough-hole, 32.768kHz VT200 G1 1 G-32.768 SEIKOCrystal,12.5p–5ppmThrough-hole, LCD LCD-JY09484 LCD1 1 LCD-JY09484A HEBEI JIYAThrough-hole, QINGZHOUVoltage JS28D20-18A T1 1 TRANS-TD28-18-3 JINSHUNTransformerThrough-hole, Back C01W-7131-6 D111 1 BG-ST-7131 SHENZHEN SAITELight PanelThrough-hole, ER14250AH BAT3 1 B-CR1/2AA YIWEIlithium batteryThrough-hole, 6*6*4.3 K1, K2 2 RESET ZhongchengButtonThrough-hole, KF-508 K3 1 KFT-5.8 ZhongchengMicro-SwitchThrough-hole, ESAM2605 U131 1 DIP-8 CSGESAMThrough-hole,Electrolytic 100 U / 35 V C221 1 D-D-F 6.3*0.5*2.50 YageoCapacitorThrough-hole,Electrolytic 220 U / 16 V C224 1 D*D*F 6.3*0.5*2.5 YageoCapacitorThrough-hole,Electrolytic 470 U / 16 V C229 1 D*D*F 8*0.6*3.5 YageoCapacitorThrough-hole,Electrolytic 1000 U / 35 V C225 1 D*D*F 12.5*0.6*5.0 YageoCapacitorThrough-hole, 1N4744A ZD23 1 DO41-UP ChangjiangZener diodeThrough-hole, 20K681 RV31 1 RV20K681 FNRPiezoresistorThrough-hole, U2, U3, U51, U52,PC817C 5 DIP-4 ToshibaOptocoupler U79Through-hole, Bead B62 Z24, Z25 2 B62A YageoThrough-hole, MZ4-250 PT7 1 PTC-120/120-35MA YageoThermistorThrough-hole, MZ6-51R RT3 1 PTC-120/120-35MA YageoThermistorThrough-hole, TVS P6KE6.8CA TV1 1 TVSUP FairchildThrough-hole, TVS P6KE22CA TV33 1 TVSUP FairchildThrough-hole, HM238 U6 1 TSOP1838 AbleirInfrared ReaderThrough-hole, AT205B D5 1 LED-5 AbleirInfrared Sender

201 TypeE-meter Case 1 QUANSHENG10（60）ARelay GRT508FA 250 uΩ 1 GELEITE



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Current transformer 10（60）/ 5 MA 1 ShenkePCB Board 1

8.3 Layer PlotsTo download the layer plots, see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.

Figure 16. Top Silkscreen Figure 17. Top Layer



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Figure 18. Bottom Layer Figure 19. Bottom Silkscreen

Figure 20. Mechanical Dimensions



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8.4 Altium ProjectTo download the Altium project files, see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.

8.5 Gerber FilesTo download the Gerber files, see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.

8.6 Software FilesTo download the software files, see the design files at http://www.ti.com/tool/TIDM-TEMPCOMPENSATED-RTC.

8.7 References

1. MSP430x5xx and MSP430x6xx Family User's Guide (Rev. K) (SLAU208N)2. MSP430F673x, MSP430F672x Mixed Signal Microcontroller (Rev. B) (MSP430f6736)



http://www.ti.com







http://www.ti.com/litv/pdf/slau208n

http://www.ti.com/lit/gpn/msp430f6736


About the Author www.ti.com

9 About the AuthorALEX CHENG joined TI in 2010 as an MCU FAE supporting MSP430 and industry metering applicationsin China. In 2011 he integrated the MCU SAE team for application system development into China. In2014, he joined the Shenzhen EP FAE team to support general MCU and WCS products. Alex Chengworks across multiple product families and technologies to leverage the best solutions possible for systemlevel application design and support. Alex Cheng graduated from Guilin University of Technology with abachelor's degree, and he received his master's degree from Shenzhen University.



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