User's Interface - Motorola M68HC08 Manual

Hardware Design
5.2.4 Power Line Input with DC-Bus Voltage Sensing
Designer Reference Manual
40
Freescale Semiconductor, Inc.
is connected to Port PTA3 also through a jumper. The jumpers enable
connection of an external user interface to MCU pins PTA3 and
PTA4/AD2 if desired. Please be aware that maximal applicable voltage
to both MCU pins is +5Vdc.
The pin PTA4 serves for programming the Flash using Flash bootloader.
After Reset, the bootloader attempts to communicate through selected
pin (PTA3). If there is a response from the programmer, the Flash can
be programmed through this pin. If there is no response, after a defined
time-out the user's program is entered. When using the serial bootloder,
the ceramic capacitor C16 should be removed.
+5V
P1
5k
GND
Figure 5-5. User's Interface
Main power supply needs to be connected to power supply terminal. The
schematics are shown in
for short circuit protection. An input capacitor C17 and open former
suppression choke L1 provides power supply filtering. The choke is
rated for 8 Amps. Unipolar transient voltage suppressor D5 protects
against power supply voltage peaks higher than 60V.
Feedback signal proportional to DC-Bus voltage is provided for the
microcontroller. DC-Bus voltage is scaled down by a voltage divider
Hardware Design
For More Information On This Product,
Go to: www.freescale.com
C16
10nF
R50
GND
1k
J3
5 6
+5V GND
3 4
1 2
Header
Figure 8-2. Power
PTA4 / AD2
PTA3
SW1
RUN/STOP
1
2
3
GND
Stage. A fuse F1 is used
DRM046 — Rev 0
MOTOROLA