W78LE51C Datasheet, PDF (8/23 Pages) Winbond – 8-BIT MICROCONTROLLER

W78LE51C/W78L051C
WIDL
IDLE
OSC
1/12
ENW
EXTERNAL
RESET
PRESCALER
14-BIT TIMER
CLEAR
INTERNAL
RESET
Watchdog Timer Block Diagram
CLRW
Typical Watch-Dog time-out period when OSC = 20 MHz
PS2 PS1 PS0
00 0
01 0
00 1
01 1
10 0
10 1
11 0
11 1
WATCHDOG TIME-OUT PERIOD
19.66 mS
39.32 mS
78.64 mS
157.28 mS
314.57mS
629.14 mS
1.25 S
2.50 S
Clock
The W78L051C 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 W78L051C relatively insensitive to duty
cycle variations in the clock. The W78L051C 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.
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