HT56RB688_13 datasheet(101/164 Pages) HOLTEK

101 / 164 page

More information regarding external reset circuits is located in Application Note HA0075E on the

Holtek website.

· RES Pin Reset

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

pulled low by external hardware such as an external switch. In this case as in the case of other reset,

the Program Counter will reset to zero and program execution initiated from this point.

· Low Voltage Reset - LVR

The microcontroller contains a low voltage reset circuit in order to monitor the supply voltage of the

device, which is selected via a configuration option. If the supply voltage of the device drops to within a

range of 0.9V~V

LVR such as might occur when changing the battery, the LVR will automatically reset the

device internally. The LVR includes the following specifications: For a valid LVR signal, a low voltage,

i.e., a voltage in the range between 0.9V~V

LVR must exist for greater than the value tLVR specified in the

A.C. characteristics. If the low voltage state does not exceed 1ms, the LVR will ignore it and will not

perform a reset function. One of a range of specified voltage values for V

LVR can be selected using

configuration options. The V

LVR value will be selected as a pair in conjunction with a Low Voltage Detect

value.

HT56RB688

TinyPowerTM A/D type Smart Card OTP MCU

with LCD, DAC, ISO 7816 and USB Interfaces

Rev. 1.10

101

April 15, 2013

R E S

S S T T i m e - o u t

C h i p R e s e t

0 . 9 V D D

0 . 4 V D D

t R S T D

RES Reset Timing Chart

R E S / P C 7

0 . 1 ~ 1 m F

1 0 k W ~

1 0 0 k W

V D D

V S S

0 . 0 1 m F * *

V D D

1 N 4 1 4 8 *

3 0 0 W *

Note:

²*² It is recommended that this component is added for added ESD protection

²**² It is recommended that this component is added in environments where power line noise is significant

External RES Circuit

L V R

S S T T i m e - o u t

C h i p R e s e t

t R S T D

Low Voltage Reset Timing Chart

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