w78e051c Winbond Electronics Corp America, w78e051c Datasheet - Page 8

• Manufacturer Part Number: w78e051c
• Description: 8-bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

Typical Watch-dog time-out period when OSC = 20 MHz
5.4 Clock
The W78E051C 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 W78E051C relatively insensitive to duty
cycle variations in the clock. The W78E051C 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.
WIDL
IDLE
Watchdog Timer Block Diagram
OSC
PS2 PS1 PS0
0
0
0
0
1
1
1
1
1/12
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
ENW
PRESCALER
- 8 -
CLRW
WATCHDOG TIME-OUT PERIOD
EXTERNAL
RESET
14-BIT TIMER
157.28 mS
314.57 mS
629.14 mS
W78E51C/W78E051C
19.66 mS
39.32 mS
78.64 mS
1.25 S
2.50 S
CLEAR
INTERNAL
RESET