ELAN Home Systems EM78P458AM, EM78P459AK Power-on Considerations, External Power on Reset Circuit

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EM78P458/459

OTP ROM

4.13 Power-on Considerations

Any microcontroller is not warranted to start proper operation before the power supply stabilizes in steady state.

EM78P458/459 POR voltage range is 1.2V~1.8V. Under customer application, when power is OFF, Vdd must drop to below 1.2V and remains OFF for 10us before power can be switched ON again. This way, the EM78P458/459 will reset and work normally. The extra external reset circuit will work well if Vdd can rise at very fast speed (50 ms or less). However, under most cases where critical applications are involved, extra devices are required to assist in solving the power-up problems.

1. External Power on Reset Circuit

The circuit shown in Fig IV.13.1-1 implements an external RC to produce a reset pulse. The pulse width (time constant) should be kept long enough to allow Vdd to reach minimum operation voltage. This circuit is used when the power supply has a slow rise time. Because the current leakage from the /RESET pin is about ±5∝A, it is recommended that R should not be great than 40 K. In this way, the voltage at Pin /RESET is held below 0.2V. The diode (D) acts as a short circuit at power-down. The capacitor, C, is discharged rapidly and fully. Rin, the current-limited resistor, prevents high current discharge or ESD (electrostatic discharge) from flowing into Pin /RESET.

VDD

 

 

/RESET

R

D

 

 

EM78P458

 

 

EM78P459

Rin

 

 

 

 

C

 

Fig. 24 External Power on Reset Circuit

2. Residue-Voltage Protection

When battery is replaced, device power (Vdd) is taken off but residue-voltage remains. The residue-voltage may trips below Vdd minimum, but not to zero. This condition may cause a poor power on reset. Fig. 25 and Fig. 26 show how to build a residue-voltage protection circuit

This specification is subject to change without prior notice.

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Contents EM78P458/459 BIT MICRO-CONTROLLEREM78P458/459 Application NoteGeneral Description Features EM78P458/459 PIN Assignment EM78P459 Pin Description R0 Indirect Addressing Register Function DescriptionOperational Registers R1 Time Clock /CounterProgram Counter Organization R5 ~ R6 Port 5 ~ Port R3 Status RegisterR4 RAM Select Register R7 ~ R8Data Memory Configuration 10. RB R9 Adcon Analog to Digital ControlRA Addata the converted value of ADC 11. RCRF Interrupt Status Register Special Purpose Registers13. RE 15. R10 ~ R3FInte INT PAB PSR2 PSR1 PSR0 Control RegisterIOC50 ~ IOC60 I/O Port Control Register Bit 0 PSR0 ~ Bit 2 PSR2 TCC/WDT prescaler bitsVrefs COE IMS2 IMS1 IMS0 CKR1 CKR0 IOC90 Gcon I/O Configuration & Control of ADCOP2E OP1E Bit4Bit2 IMS2IMS0 Description of AD Configuration Control BitsIOCB0 Pull-down Control Register IMS2IMS0IOCC0 Open-Drain Control Register IOCD0 Pull-high Control RegisterWdte EIS IOCE0 WDT Control RegisterIOCF0 Interrupt Mask Register Cmpie PWM2IE PWM1IE Adie Exie Icie TcieIOC51 Pwmcon PWM2E PWM1E T2EN T1ENBit 5Bit 3 VOF12VOF10 Offset voltage bits IOC81 PRD1 Period of PWM1CALI1 SIGN1 CALI2 SIGN2IOCB1 PRD2 Period of PWM2 Bit 5Bit 3 VOF22VOF20 Offset voltage bitsTCC/WDT & Prescaler Block Diagram of TCC and WDT I/O PortsCcircuit of I/O Port and I/O Control Register for Port Circuit of I/O Port and I/O Control Register for P60~P67 Usage of Port 6 Input Changed Wake-up/Interrupt Function Reset and Wake-upFunction of Reset and Wake-up Contw CLR R1 Status of T, and P of Status Register Values of RST, T, and P after Reset Status of RST, T and P being Affected by EventsInterrupt Analog-To-Digital Converter ADC Interrupt Input CircuitADC Control Register ADCON/R9, AD-CMP-CON/IOCA0, GCON/IOC90 BIT Symbol Iocs Adrun Adpd ADIS2 ADIS1 ADIS0BIT Symbol Vrefs COE IMS2 IMS1 IMS0 CKR1 CKR0 ADCON/R9GCON/IOC90 ADC Data Register ADDATA/RACKR1 and CKR0 Bit 1 and Bit 0 The conversion time select Shows the Gains and the Operating Range of ADCD Conversion Time D Operation During Sleep ModeD Sampling Time Programming Steps/ConsiderationsDemonstration Programs CINT== 0XFIocs Adrun Adpd ADIS2 ADIS1 ADIS0 Dual Sets of PWM Pulse Width Modulation OverviewIncrement Timer Counter Tmrx TMR1H/TWR1L or TMR2H/TWR2L Functional Block Diagram of the Dual PWMsComparator PWM Programming Procedures/StepsPWM Period Prdx PRD1 or PRD2 Period = Prdx + 1 * 4 * 1/Fosc * Tmrx prescale valueTMR1X and TMR2X TMR1H/TWR1L and TMR2H/TMR2L TimerFunction description Prdx PRD1 and PRD2 PWM period registerComparator Timer programming procedures/stepsExternal Reference Signal Programming the Related RegistersInterrupt Using as An Operation AmplifierWake-up from Sleep Mode Initialized Values after Reset Summary of the Initialized Values for RegistersCALI1 SIGN1 Oscillator Oscillator ModesEM78P458 Crystal Oscillator/Ceramic Resonators XtalSummary of Maximum Operating Speeds EM78P459EM78P458 EM78P459 HXTLXT VddExternal RC Oscillator Mode RC Oscillator Mode with Internal Capacitor EM78P458 EM78P459 Vcc RextResidue-Voltage Protection Power-on ConsiderationsExternal Power on Reset Circuit EM78P458 EM78P459 RinCode Option Register Word Enwdt Clks PTB HLF RCT HLPBit 5 ~ Bit 0 ID5~ID0 Customer’s ID Bit 11 ~ Bit 9 VOF22~VOF20 Offset voltage bitsInstruction Set List of the instruction set of EM78P458/459ADD A,R AC Test Input/Output Waveform Timing DiagramsReset Timing CLK=0 TCC Input Timing CLKS=0Absolute Maximum Ratings Electrical Characteristics Crystal type, two clocksComparatorOP CharacteristicVdd = 5.0V,Vss=0V,Ta=0 to AC Electrical CharacteristicTa=0C ~ 70 C, VDD=5V±5%, VSS=0VIVR OTP MCU AppendixPackage Types DIP

EM78P458, EM78P459AM, EM78P458AM, EM78P459AK, EM78P459 specifications

ELAN Home Systems offers a range of advanced microcontrollers, including the EM78P458AP, EM78P459, EM78P459AK, EM78P458AM, and EM78P459AM, that cater to various applications in the consumer electronics sector. These microcontrollers are known for their high efficiency, low power consumption, and robust performance, making them ideal for a wide range of smart home devices.

The EM78P458AP and EM78P459 models feature an 8-bit architecture, enabling efficient processing for applications requiring moderate complexity. They are equipped with a variety of I/O options, including GPIO, UART, and ADC, facilitating seamless integration with numerous peripherals. This flexibility allows developers to create customized solutions tailored to specific user needs.

One of the main highlights of these microcontrollers is their low-power operation, which is essential for battery-operated devices. This is particularly appealing in smart home contexts, where devices are expected to maintain long operational lifetimes without frequent battery replacements. The EM78P458AP and EM78P459 series prioritize energy efficiency, ensuring that they consume minimal power during both active and idle states.

In terms of memory, these microcontrollers also provide substantial ROM and RAM capacities, which enhance their ability to handle complex programs and data. The EM78P459AK variant adds additional features that empower developers with greater flexibility in terms of code storage and execution.

Another critical aspect of these microcontrollers is their built-in protection mechanisms, including voltage and thermal protection, which ensure safe operations under varying environmental conditions. This is vital for home automation systems, where device reliability is paramount to user satisfaction.

The EM78P458AM and EM78P459AM models further extend the family with added functionalities, such as enhanced communication capabilities featuring protocols like I2C and SPI. This facilitates robust inter-device communication, making it easier to integrate various smart home devices into a cohesive network.

Overall, ELAN Home Systems’ EM78P458 and EM78P459 series microcontrollers stand out for their versatile application potential, low power consumption, and reliability. With their innovative technologies and characteristics, they are well-suited for driving the next generation of smart home solutions, ensuring convenience, efficiency, and connectivity for users worldwide.
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