Holtek HT48R05A-1, Handbook, Page: 42 / 125

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 re-
set, 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 automati-
cally reset the device internally. For a valid LVR signal, a low voltage, i.e. a voltage in the range be-
tween 0.9V~V
LVR
must exist for greater than 1ms. If the low voltage state does not exceed 1ms,
the LVR will ignore it and will not perform a reset function.
Watchdog Time-out Reset during Normal Operation
The Watchdog time-out reset during normal operation is the same as RES reset except that the
Watchdog time-out flag TO will be set to
²
1
²
.
Chapter 1 Hardware Structure
35
L V R
S S T T i m e - o u t
I n t e r n a l R e s e t
t
R S T D
Low Voltage Reset Timing Chart
R E S
S S T T i m e - o u t
I n t e r n a l R e s e t
0 . 9 V
D D
0 . 4 V
D D
t
R S T D
RES Reset Timing Chart
W D T T i m e - o u t
S S T T i m e - o u t
I n t e r n a l R e s e t
t
R S T D
WDT Time-out Reset during Normal Operation Timing Chart