
PICDEM 4 User’s Guide
A.13 REAL-TIME CLOCK
This circuit allows the user to configure a PICmicro MCU in either the U7 or U8 socket
for timekeeping, using a 32.768 kHz clock crystal connected to Timer1’s T1OSO and
T1OSI pins. ICD operation will not be functional when the Real-Time Clock circuit is
enabled. For RTC operation, these jumpers must be configured as follows:
? J7 - ON
? J9 - ON
? J21 - OFF
A.14 LCD DISPLAY
An LCD display with two lines, 16 characters per line, is connected to the I/O Expander
(U3), which can be driven by all three device sockets.
A 10K pot may be installed into R4 to adjust contrast on the LCD. If this is done, R5 and
R6 need to be removed.
The LCD is connected to the I/O Expander by three control lines (E, R/W, RS), and four
data lines (DB7:DB4). For LCD operation, these jumpers must be configured as
follows:
PIC16
? J8/10 - Upper two pins ON
? J21 - OFF (PORTB LEDs)
PIC18
? J8/10 - Lower two pins ON
? J21 - OFF (PORTB LEDs)
DS51337A-page 18
? 2003 Microchip Technology Inc.