Holtek HT46R003B Manual page 27

HT46R003B
Cost-Effective A/D 8-bit OTP MCU
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 minimize any stray noise interference.
For applications that operate within an environment where more noise is present the reset circuit
shown is recommended.
Note: "*' It is recommended that this component is added for added ESD protection.
"**" It is recommended that this component is added in environments where power line
noise is significant.
More information regarding external reset circuits is located in Application Note HA0075E on the
Holtek website.
This type of reset occurs when the microcontroller is already running and the RES pin is forcefully
pulled low by software control using the register EXTRESB. In this case of other reset, the Program
Counter will reset to zero and program execution initiated from this point.
• EXTRESB Register
Bit 7
Name —
R/W —
POR —
Bit 7~5 Unimplemented, read as "0"
Bit 4~0 RESBEN4~RESBEN0: PA7/RES selection
00000: PA7
10101: RES
Other values: MCU reset
Rev. 1.00
V
D D
0 . 0 1 m F * *
1 N 4 1 4 8 *
1 0 k W ~
1 0 0 k W
3 0 0 W *
0 . 1 ~ 1 m F
External RES Circuit
0 . 4 V
D D
R E S
I n t e r n a l R e s e t
Note: t is power-on delay, typical time=50ms
RSTD
RES Reset Timing Chart
6 5 4
— — RESBEN� RESBEN3 RESBEN� RESBEN1 RESBEN0
— — R/W
— — 0
�7
V D D
R E S / P A 7
V S S
0 . 9 V
D D
t t
R S T D + S S T
3 2 1
R/W R/W R/W
0 0 0
��ne 1�� �01�
0
R/W
0