mc68hc05l25 Freescale Semiconductor, Inc, mc68hc05l25 Datasheet - Page 20

• Manufacturer Part Number: mc68hc05l25
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

General Description
1.5.1 V
Power is supplied to the MCU through V
MCU operates from a single power supply.
Very fast signal transitions occur on the MCU pins. The short rise and fall times place very high
short-duration current demands on the power supply. To prevent noise problems, special care should be
taken to provide good power supply bypassing at the MCU by using bypass capacitors with good
high-frequency characteristics that are positioned as close to the MCU as possible. Bypassing
requirements vary, depending on how heavily the MCU pins are loaded.
1.5.2 V
This pin provides an offset to the LCD driver bias for adjusting the contrast of LCD. See
Driver
1.5.3 RESET
This pin can be used as an input to reset the MCU to a known startup state by pulling it to the low state.
The RESET pin contains a steering diode to discharge any voltage on the pin to V
removed. The RESET pin contains an internal Schmitt trigger to improve its noise immunity as an input.
Refer to
1.5.4 OSC1 and OSC2
The OSC1 and OSC2 pins are the connections for the 2-pin on-chip oscillator. The OSC1 and OSC2 pins
can accept these sets of components:
The frequency, f
operating frequency, f
20
1. A crystal or ceramic resonator as shown in
2. An external clock signal as shown in
for additional information.
DD
LCD
Chapter 5
and V
OSC
MASK OPTION
SS
Resets.
, of the oscillator or external clock source is divided by two to produce the internal
OP
, by default.
C
O1
(a) Crystal Connections
Figure 1-4. Oscillator Connections
OSC1
4 MHz (TYPICAL)
MC68HC05L25 Data Sheet, Rev. 3.1
DD
MCU
R
OF
and V
Figure
C
O2
OSC2
SS
Figure
1-4(b)
. V
DD
1-4(a)
is the positive supply, and V
OSC1
Source Connection
(b) External Clock
EXTERNAL CLOCK
MCU
UNCONNECTED
OSC2
DD
Freescale Semiconductor
when the power is
SS
Chapter 11 LCD
is ground. The