Arizona Picdem 17 - Manual (Page 11)

 2001 Microchip Technology Inc. DS39024B-page 5
About PICDEM 17 Demonstration Board
1.8 Oscillator Options
The PICDEM 17 demonstration board layout will only accept a canned
oscillator. The use of a crystal or ceramic resonator requires that the user
modify the board.
1.9 RS-232 Serial Ports
The PICDEM 17 demonstration board supports both USARTs on the
PIC17C7XX devices. A level shifting IC is used to convert from the TTL/
CMOS levels out of the PIC17C7XX to the RS-232 voltages. USART2 also
has the capability to function in a hardware handshaking mode using RTS and
CTS. These signals are level shifted and connected to PORTB pins 4 (CTS)
and 5 (RTS).
1.10 Push-button Switches
The PICDEM 17 demonstration board has 8 general purpose push-button
switches that are available to the user. These switches are not connected
directly to I/O pins on the microcontroller but are memory mapped into the
address space. The switches are available at address FFFCh.
1.11 LEDs
The PICDEM 17 demonstration board also has 8 LEDs which are also
memory mapped. These LEDs may be accessed at address FFFDh. There is
no read capability for the LEDs, so the user must have a shadow register in
the PIC17C7XX device to keep track of the value on the latch.
1.12 Analog Circuitry
In addition to the power and ground planes on the PICDEM 17 demonstration
board, it also has separate analog and digital power supplies. Both of these
voltage regulators use connector J1 as the source. If the user desires to
power the board from the test points in the prototyping areas, then both sets
of test points in the analog and digital must be used. Otherwise one portion of
the board will not be operational.
1.13 External LCD Interface
The PICDEM 17 demonstration board provides an interface to an external
LCD display that uses the Hitachi HD4478 LCD controller or equivalent
device. The LCD is used in the 4-bit interface mode. Four data lines and three
control lines are required to operate the LCD. These LCD signals are
multiplexed with some of the A/D converter channels. It is therefore important
that the A/D is properly initialized before the LCD can be used (refer to
Chapter 4). The board layout provides space for the Optrex DMC-50448N 8x2
character display which is available from DigiKey.