w78l812a Winbond Electronics Corp America, w78l812a Datasheet - Page 13

• Manufacturer Part Number: w78l812a
• Description: 8-bit Mcu Series 80c51-based
• Manufacturer: Winbond Electronics Corp America

Typical Watch-Dog time-out period when OSC = 20 MHz
5.7
The W78L812 is designed to be used with either a crystal oscillator or an external clock. Internally, the
clock is divided by two before it is used. This makes the W78L812 relatively insensitive to duty cycle
variations in the clock. The W78L812 incorporates a built-in crystal oscillator. To make the oscillator
work, a crystal must be connected across pins XTAL1 and XTAL2. In addition, a load capacitor must
be connected from each pin to ground. An external clock source should be connected to pin XTAL1.
Pin XTAL2 should be left unconnected. The XTAL1 input is a CMOS-type input, as required by the
crystal oscillator.
5.8
5.8.1
The idle mode is entered by setting the IDL bit in the PCON register. In the idle mode, the internal
clock to the processor is stopped. The peripherals and the interrupt logic continue to be clocked. The
processor will exit idle mode when either an interrupt or a reset occurs.
Clock
Power Management
Idle Mode
WIDL
IDLE
Watchdog Timer Block Diagram
PS2 PS1 PS0
OSC
0
0
0
0
1
1
1
1
0
1
0
1
0
0
1
1
1/12
0
0
1
1
0
1
0
1
ENW
PRESCALER
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CLRW
WATCHDOG TIME-OUT PERIOD
EXTERNAL
RESET
Publication Release Date: November 6, 2006
W78LE812/W78L812A
14-BIT TIMER
157.28 mS
314.57 mS
629.14 mS
19.66 mS
39.32 mS
78.64 mS
CLEAR
1.25 S
2.50 S
INTERNAL
RESET
Revision A9