Oscillator Options; Serial Eeprom - Microchip Technology Explorer 16 User Manual

Explorer 16 Development Board User's Guide
FIGURE 4-1:
4.2.8
The Explorer 16 also has a footprint and layout support for the Optrex 128 x 64 dot-matrix
graphic LCD (part number F-51320GNB-LW-AB) and associated circuitry. This is the
same display used in Microchip's MPLAB PM3 programmer.
4.2.9
Five push button switches provide the following functions:
• S1: Active-low MCLR switch to hard reset the processor
• S3: Active-low switch connected to RD6 (user-defined)
• S4: Active-low switch connected to RD13 (user-defined)
• S5: Active-low switch connected to RA7 (user-defined)
• S6: Active-low switch connected to RD7 (user-defined)
Switch S1 has a debounce capacitor, whereas S3 through S6 do not; this allows the
user to investigate debounce techniques. When Idle, the switches are pulled high
(+3.3V). When pressed, they are grounded.
4.2.10
A 10 kΩ potentiometer is connected through a series resistor to AN5. It can be adjusted
from V
4.2.11
Eight red LEDs (D2 through D9) are connected to PORTA of the PIM socket. The
PORTA pins are set high to light the LEDs. These LEDs may be disabled by removing
jumper JP2.
4.2.12
The installed microcontroller has two separate oscillator circuits connected.The main
oscillator uses an 8 MHz crystal (Y3) and functions as the controller's primary oscillator.
A second circuit, using a 32.768 kHz (watch type) crystal (Y2), functions as the Timer1
oscillator and serves as the source for the RTCC and secondary oscillator.
The PIC18LF4550, at the heart of the USB subsystem, is independently clocked and
has its own 20 MHz crystal (Y1).
4.2.13
A 25LC256 256K (32K x 8) serial EEPROM (U5) is included for nonvolatile firmware
storage. It is also used to demonstrate SPI bus operation.
DS51589A-page 29
MODIFICATIONS TO R60-R67 FOR LCD CONFIGURATION
(SCALE ENHANCED FOR VISIBILITY)
Cut Traces
Here
Graphic LCD
Switches
Analog Input (Potentiometer)
to GND to provide an analog input to one of the controller's A/D channels.
DD
LEDs

Oscillator Options

Serial EEPROM

Add
Solder
Bridges
Here
© 2005 Microchip Technology Inc.