sh66k51a SinoWealth Micro-Electronics Corp. Ltd, sh66k51a Datasheet - Page 30

• Manufacturer Part Number: sh66k51a
• Description: 2k 4-bit Micro-controller With Lcd Driver
• Manufacturer: SinoWealth Micro-Electronics Corp. Ltd

12. Low Voltage Reset (LVR)
The LVR function is to monitor the supply voltage and generate an internal reset in the device. It is typically used in AC line
applications or large battery where large loads may be switched in and cause the device voltage to temporarily fall below
the specified operating minimum.
The LVR circuit has the following functions:
- Generates a system reset when V
- Cancels the system reset when V
13. Low Power Detect (LPD)
The LPD function monitors the supply voltage of the battery
Functions of LPD Circuit:
The LPD circuit has the following functions:
LPD bit = 1 when V
LPD bit = 0 when V
14. Watchdog Timer
Watchdog timer is a down-count counter, and its clock source is OSC clock (32.768kHz Crystal or 131kHz RC) and will not
run in the STOP mode. The watchdog timer automatically generates a device reset when it overflows. It can be enabled or
disabled permanently by using the Code Option.
The watchdog timer control bits ($1E bit2 - bit0) are used to select different overflow frequency. The watchdog timer
overflow flag ($1E bit3) will be automatically set to “1” by hardware when the watchdog timer overflows. And the flag ($1E
bit3) will be clear to “0” when read $1E. By reading or writing the system register $1E, the watchdog timer should re-count
before the overflow happens.
System Register $1E: Watchdog Timer (WDT)
Note:
Watchdog timer overflow period is valid for V
Address
Address
$1E
$06
WDT
Bit 3
Bit3
X
X
X
X
X
X
X
X
0
1
-
DD
DD
≤ V
> V
WDT.2
Bit 2
LPD
LPD
Bit2
X
X
0
0
0
0
1
1
1
1
-
(= 2.3 ± 0.1V)
(= 2.3 ± 0.1V)
DD
DD
WDT.1
Bit 1
Bit1
> V
≤ V
X
X
0
0
1
1
0
0
1
1
-
LVR
LVR
DD
(= 1.7 ± 0.1V).
(= 1.7 ± 0.1V).
WDT.0
= 3V.
Bit 0
LPD
Bit0
X
X
0
1
0
1
0
1
0
1
R/W
R/W
R/W
R
R
30
Bit0 - 2: Watchdog timer control
Bit3: Watchdog timer overflow flag. (Read only)
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
Watchdog timer-out period = 2
No watchdog timer overflow reset
Watchdog timer overflow
Bit0: 2.3V LPD flag
Remarks
Remarks
17
15
13
11
10
9
8
7
/f
/f
/f
/f
/f
/f
/f
/f
OSC
OSC
OSC
OSC
OSC
OSC
OSC
OSC
SH66K51A