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variety of special functions. Features include a pair of
analog comparators; input channel multiplexer; a current
source; and a temperature sensing diode. Their simple
nature requires very little die area yet they provide capability
normally found in more expensive MCUs. This note presents
a range of applications. Topics include an analog subsystem
overview, voltage comparators, current source/discharge,
analog multiplexers, analog power-up considerations, A/D
conversion, and a design check list.
describes such a technique using a segmented display; it
can easily be adapted to other types with a few changes in
software.
Order by: AN1740/D
A simple function such as resetting an MCU during the
application or removal of power can cause many problems
if not handled properly. Symptoms can range from a slight
delay in MCU response, to very erratic and inconsistent
behavior, to total system failure. This document discusses
the main issues in respect of HC05, HC08 and HC11
devices, and leads to a safe and reliable approach to
transitioning power.
Order by: AN1743/D
Resetting Microcontrollers During Power
Transitions
In-Circuit and Emulation Considerations
for MC68HC05JJ/JP Series
Microcontrollers
The MC68HC05JJ and MC68HC05JP series of MCUs
presents a unique combination of traditional digital peripherals
and simple analog components which can be used to
implement a variety of special functions. However adding
the capability of low-level analog signals to a digital IC
creates issues not normally considered in MCU designs,
for example circuit board design and emulation considerations
connected with the level of analog accuracy. This note
discusses issues which must be considered both in the
end application and while developing software using an
emulator such as the MMDS05.
Order by: AN1744/D
Interfacing the HC705C8A to an LCD
Module
More and more applications use Liquid Crystal Displays
(LCDs) to display data. This note describes the hardware
and software interface required to display information from
the MC68HC705C8A. It uses an Optrex DMC16207 LCD
module, incorporating a Hitachi HD44780 LCD driver which
provides the LCD segment waveforms and a simple parallel
port interface. Circuitry and example code are also given
to demonstrate a means of providing pre-defined messages
from EPROM memory; the code can be modified easily to
take SPI and SCI data and display it on the LCD module.
Order by: AN1741/D
Programming the 68HC705J1A In-Circuit
The low-cost MC68HC705J1A microcontroller does not
have a built-in function to allow in-circuit programming,
which may be necessary when sections of code such as
lookup tables or calibration values need to be entered
after assembly. This note describes how in-circuit
programming can be achieved using previously programmed
‘bootloader’ code.
Order by: AN1745/D
Migrating from the MC68HC705K1 to the
MC68HC805K3
Motorola offers two devices that allow easy migration of
MC68HC705K1 applications. Depending on the specific
design, system enhancements and cost considerations,
two different migration paths are open. The MC68HC805K3
is pin for pin compatible with the MC68HC705K1 and is
roughly 90% of the cost; the MC68HC705KJ1 is not pin for
pin compatible, but is roughly 70% of the cost. This note
discusses the differences between the two devices, plus
some additional features of the MC68HC805K3.
Order by: AN1742/D
Scrolling Message Software
Many MCU applications use displays such as LCD or LED
panels to present data, and modern displays are an efficient
and affordable way for MCUs to communicate to the outside
world. However one limitation is the amount of information
that can be presented at any one time. To output a message
that is longer than its display, MCU software needs a
method of scrolling information across the screen. The
method should be divided ito independent tasks, allowing
for normal paced-loop program execution. This note
Order by: AN1747/D
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