AN2262 Motorola / Freescale Semiconductor, AN2262 Datasheet - Page 6

• Manufacturer Part Number: AN2262
• Description: Wireless HC08 Modem
• Manufacturer: Motorola / Freescale Semiconductor

AN2262/D
Power Supply
MCU Core Circuit
Input/Output
Functions
6
The D13 diode protects the complete circuit from reverse voltage.
The MCU operating voltages V
C6, C7, and C8 close to the MCU on their respective ground pins. They are all
driven from the regulated 5-volt V
The MC33491 chip requires a 3-volt power supply, provision is made for a
3-volt power supply named V
For clock generation, the external elements X1, C1, C2, C10, R4, and R5 are
used. These elements form a Pierce oscillator together with the active
elements integrated in the MCU. This oscillator produces a clock frequency of
32.768 kHz using ultra low-cost watch quartz. The internal bus clock of the
MCU (3.36864 MHz) is derived by means of the phase-locked loop (PLL) from
the main clock frequency.
For demonstration purposes, the board has:
The push buttons are connected to the three port pins PTA0, PTA1, and PTA2
and the jumpers to PTA3 and PTA4. By pushing the buttons (or closing the
jumpers), a low level is produced on the appropriate input. Since the port pins
have internal pull-up resistors, no external resistors are required. The
occurrence of the high-low edge at the respective pin of port A is an input event
which may result in the generation of a keyboard interrupt by the
MC68HC908GP32 (this feature is not used in ‘transparent’ software described
in Software).
For optical signalling, five LEDs are attached to port C (pins PTC0, PTC1,
PTC2, PTC3, and PTC4), three of them are identical to those used in the
original NET.08 demo (they are marked Red, Yellow, and Green), the next two
diodes are for generic use (marked FN1 and FN2). These port pins have a high
drive capability of up to 10 mA. Therefore, it is not necessary to use a driver.
The last two LEDs are connected to port E whose pins are shared with two
serial communication interface (SCI) lines (PTE0/TXD and PTE1/RXD).
In such a configuration the user simply gets an indication of activity on the serial
line.
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Three push buttons
Two configuration jumpers
Five + two dedicated LEDs
An optical sensor (photo resistor)
A knob
A buzzer
A power supply measurement circuit (resistor divider)
Wireless HC08 Modem
30
DD,
.
V
CC
DDA
net.
,
and V
REFH
, are supported by capacitors
MOTOROLA