HT68F14 HOLTEK [Holtek Semiconductor Inc], HT68F14 Datasheet - Page 43

• Manufacturer Part Number: HT68F14
• Description: Enhanced I/O Flash Type MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

HT68F13/HT68F14/HT68F15
Enhanced I/O Flash Type MCU
Rev. 1.10
RES Pin Reset
More information regarding external reset circuits is located in Application Note HA0075E on the
Holtek website.
Pulling the RES Pin low using external hardware will also execute a device reset. 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:
Note: t
As the reset pin is shared with PB.3, the reset function must be selected using a configuration option.
Although the microcontroller has an internal RC reset function, if the VDD power supply rise time is
not fast enough or does not stabilise quickly at power-on, the internal reset function may be
incapable of providing proper reset operation. For this reason it is recommended that an external RC
network is connected to the RES pin, whose additional time delay will ensure that the RES pin
remains low for an extended period to allow the power supply to stabilise. During this time delay,
normal operation of the microcontroller will be inhibited. After the RES line reaches a certain
voltage value, the reset delay time t
microcontroller will begin normal operation. The abbreviation SST in the figures stands for System
Start-up Timer. For most applications a resistor connected between VDD and the RES pin and a
capacitor connected between VSS and the RES pin will provide a suitable external reset circuit. Any
wiring connected to the RES 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.
RSTD
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
is power-on delay, typical time=100ms
RES Reset Timing Chart
m
RSTD
External RES Circuit
43
m
is invoked to provide an extra delay time after which the
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February 9, 2011