HT85F2270 datasheet(79/226 Pages) HOLTEK

79 / 226 page

Rev. 1.00

79 of ��6

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

RESET Pin Reset

For most applications a resistor connected between VDD and the RESET pin and a capacitor

connected between VSS and the RESET pin will provide a suitable external reset circuit. Any

wiring connected to the RESET pin should be kept as short as possible to minimise any stray noise

interference. For applications that operate within an environment where more noise is present the

Enhanced Reset Circuit shown is recommended.

RESET

VDD

0.1µF

Basic Reset Circuit

100kΩ

RESET

VDD

100kΩ

0.1μF

10kΩ

0.01μF

Enhanced Reset Circuit

This type of reset occurs when the microcontroller is already running and the RESET pin is

forcefully pulled low by external hardware such as an external switch. In this case as in the case

of other resets, the Program Counter will reset to zero and program execution initiated from this

point. Note that, during the power-up sequence, the reset circuit should make sure that the external

reset to be released after the internal power-on reset is over plus a suitable delay time. To improve

the noise immunity, the low portion of external reset signal must be greater than that specified by

tRES in the A.C. characteristics, for the internal logic to recognise a valid reset. When a RESET pin

reset takes place, the XRSTF bit in the RSTSRC register will be set high to indicate this reset.

HT85F2270 датащи(PDF) 79 Page - Holtek Semiconductor Inc