IBM EM78P447N Power On Considerations, External Power On Reset Circuit, Customer ID Register Word

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EM78P447N

8-Bit Microcontroller with OTP ROM

4.8.2 Customer ID Register (Word 1)

Word 1

Bit 12~Bit 0

XXXXXXXXXXXXX

Bit 12~0: Customer’s ID code

4.9 Power On Considerations

Any microcontroller is not guaranteed to start and operate properly before the power supply stays at its steady state. EM78P447N is equipped with Power On Voltage Detector(POVD) with a detecting level is 2.0V. It will work well if Vdd rises fast enough (10 ms or less). In many critical applications, however, extra devices are still required to assist in solving power-up problems.

4.10 External Power On Reset Circuit

The circuit shown in Fig.16 implements an external RC to produce the reset pulse. The pulse width (time constant) should be kept long enough for Vdd to reached minimum operation voltage. This circuit is used when the power supply has slow rise time. Because the current leakage from the /RESET pin is about ±5∝A, it is recommended that R should not be greater than 40 K. In this way, the /RESET pin voltage is held below 0.2V. The diode (D) acts as a short circuit at the moment of power down. The capacitor C will discharge rapidly and fully. Rin, the current-limited resistor, will prevent high current or ESD (electrostatic discharge) from flowing to pin /RESET.

Vdd
/RESET		R
/RESET		D
		D
EM78P447N
	Rin	C
		C

Fig. 13 External Power-Up Reset Circuit

28 •	Product Specification (V1.1) 03.30.2005

(This specification is subject to change without further notice)

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Contents EM78P447N Elan Microelectronics Corporation Contents Specification Revision History General Description EM78P447NBWM PIN Assignment EM78P447NAS Pin Description Symbol Pin No Type FunctionEM78P447NAP and EM78P447NAM Pin Description EM78P447NCK and EN78P447NCM Pin Description Power supplyEM78P447NBP and EM78P447NBWM Pin Description Function Description EM78P447NDK and EM78P447NDM Pin DescriptionOperational Registers 1 R0 Indirect Addressing Register2 R1 Time Clock /Counter 3 R2 Program Counter & StackCall RET Retl Reti FffhData Memory Configuration 5 R4 RAM Select Register 6 R5~R7 Port 5 ~ Port77 R8~R1F and R20~R3E General Purpose Register R5, R6 and R7 are I/O registersSpecial Purpose Registers 8 R3F Interrupt Status RegisterAccumulator Control Register3 IOC5 ~ IOC7 I/O Port Control Register Iocb Wake-up Control Register for Port6TCC Rate WDT RateIoce WDT Control Register WUEIocf Interrupt Mask Register ExieTCC and WDT Block Diagram TCC/WDT & PrescalerI/O Ports IODReset and Wake-up ResetUsage of Sleep1 and Sleep2 Mode SLEEP2 SLEEP1Address Name Reset Type Bit Summary of the Initialized Values for RegistersR3FISR Exif TcifWUE7 WUE6 WUE5 WUE4 IocbPrevious status before reset Previous value before resetStatus of RST, T, and P of Status Register Events that may Affect the T and P StatusController Reset Block Diagram InterruptMode OscillatorOscillator Modes Crystal Oscillator/Ceramic ResonatorsXTAL Summary of Maximum Operating SpeedsConditions Fxt max.MHzExternal RC Oscillator Mode Oscillator Type Frequency Mode C1pF C2pFHXT LXTCode Option Register Code Option Register WordPR2~PR0 are protect bits, protect type as following ProtectPower On Considerations External Power On Reset CircuitCustomer ID Register Word Bit 12~0 Customer’s ID codeReset Residue-Voltage ProtectionInstruction Set NOP DAAContw SlepDjza R DJZ RRrca R RRC RTiming Diagram AC Test Input/Output W aveformDC Electrical Characteristic Symbol Parameter Condition Min Typ Max UnitTa= 25 C, VDD= 5.0V±5%, VSS= Items RatingTa=- -40 C ~ 85 C, VDD=5V ±5%, VSS=0V AC Electrical CharacteristicSymbol Parameter Conditions Min Typ Max Unit Device characteristic Vih, Vil of TCC, /INT, /RESET PinPort5, Port6 Port7 Voh vs. Ioh,VDD=5V Port5, Port6, and Port7 Voh vs. Ioh, VDD=3V Vol/Iol VDD=5V Vol/Iol VDD=3V Vol/Iol 100 Vol/Iol WDT Cext=100pF, Typical RC OSC Frequency Typical ICC1 and ICC2 vs. Temperature Maximum ICC1 and ICC2 vs. Temperature Typical ISB1 and ISB2 vs. Temperature Maximum ISB1 and ISB2 vs. Temperature EM78P447N HXT ImA Lead plastic dual inline package（DIP）－ 300 mil Package Type Pin Count Package SizeLead plastic dual inline skinny package（DIP）－ 300 mil Lead plastic dual inline package（DIP）－ 600 mil838 27TYP EM78P447N