HT46R02N HOLTEK [Holtek Semiconductor Inc], HT46R02N Datasheet - Page 26

• Manufacturer Part Number: HT46R02N
• Description: Small Package 8-Bit OTP MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Note:
Note: t
Note: t
Rev.1.00
For applications that operate within an environment
where more noise is present the Enhanced Reset Cir-
cuit shown is recommended.
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 initi-
ated from this point.
Low Voltage Reset
The microcontroller contains a low voltage reset cir-
cuit in order to monitor the supply voltage of the de-
vice. The LVR function is selected via a configuration
option. If the supply voltage of the device drops to
within a range of 0.9V~V
changing the battery, the LVR will automatically reset
the device internally. For a valid LVR signal, a low sup-
ply voltage, i.e., a voltage in the range between
0.9V~V
ified by t
ply voltage state does not exceed this value, the LVR
RSTD
RSTD
added for added ESD protection
added in environments where power line noise
is significant
* It is recommended that this component is
** It is recommended that this component is
LVR
Low Voltage Reset Timing Chart
LVR
is power-on delay, typical time=100ms
is power-on delay, typical time=100ms
must exist for a time greater than that spec-
in the A.C. characteristics. If the low sup-
RES Reset Timing Chart
External RES Circuit
LVR
LVR
such as might occur when
26
Note: t
Note:
Reset Initial Conditions
The different types of reset described affect the reset
flags in different ways. These flags, known as PDF and
TO are located in the status register and are controlled
by various microcontroller operations, such as the Sleep
function or Watchdog Timer. The reset flags are shown
in the table:
Note: u stands for unchanged
will ignore the low supply voltage and will not perform
a reset function. The actual V
lected via configuration options.
Watchdog Time-out Reset during Normal Operation
The Watchdog time-out Reset during normal opera-
tion is the same as a hardware RES pin reset except
that the Watchdog time-out flag TO will be set to 1 .
Watchdog Time-out Reset during Sleep mode
The Watchdog time-out Reset during Sleep mode is a
little different from other kinds of reset. Most of the
conditions remain unchanged except that the Pro-
gram Counter and the Stack Pointer will be cleared to
Characteristics for t
TO
WDT Time-out Reset during Normal Operation
0 and the TO flag will be set to 1 . Refer to the A.C.
0
u
1
1
RSTD
PDF
The t
clock cycles via configuration option if the sys-
tem clock source is provided by ERC or HIRC.
The SST is 1024 for HXT or LXT.
WDT Time-out Reset during Sleep
0
u
u
1
is power-on delay, typical time=100ms
SST
Power-on reset
RES or LVR reset during Normal or Slow
Mode operation
WDT time-out reset during Normal or
Slow Mode operation
WDT time-out reset during Sleep Mode
operation
can be chosen to be either 1024 or 2
HT46R01B/02B/01N/02N
HT48R01B/02B/01N/02N
Timing Chart
Timing Chart
SST
RESET Conditions
details.
LVR
December 15, 2009
value can be se-