ht82m75r Holtek Semiconductor Inc., ht82m75r Datasheet - Page 25

• Manufacturer Part Number: ht82m75r
• Description: I/o Type 8-bit Otp Mcu
• Manufacturer: Holtek Semiconductor Inc.

Rev. 1.10
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
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 Power Down
The Watchdog time-out Reset during Power Down 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
WDT Time-out Reset during Normal Operation
0 and the TO flag will be set to 1 . Refer to the A.C.
WDT Time-out Reset during Power Down
LVR
Low Voltage Reset Timing Chart
LVR
must exist for a time greater than that spec-
in the A.C. characteristics. If the low sup-
Timing Chart
Timing Chart
SST
LVR
details.
LVR
such as might occur when
LVR
value can be se-
25
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
Power Down function or Watchdog Timer. The reset
flags are shown in the table:
Note:
The following table indicates the way in which the vari-
ous components of the microcontroller are affected after
a power-on reset occurs.
TO PDF
Program Counter
Interrupts
WDT
Timer/Event
Counter
Input/Output Ports I/O ports will be setup as inputs
Stack Pointer
0
0
u
1
1
u stands for unchanged
0
1
u
u
1
Item
RES reset during power-on
RES wake-up HALT
RES or LVR reset during normal operation
WDT time-out reset during normal operation
WDT time-out reset during Power Down
HT82M75R/HT82M75RE
HT82K75R/HT82K75RE
Reset to zero
All interrupts will be disabled
Clear after reset, WDT begins
counting
Timer Counter will be turned off
Stack Pointer will point to the top
of the stack
RESET Conditions
Condition After RESET
June 11, 2010