
71M6521 Demo Board User’s Manual
Page: 62 of 111
© 2005-2009 TERIDIAN Semiconductor Corporation
Revision 2.18
2.3.3 EEPROM
EEPROMs should be connected to the pins DIO4 and DIO5 (see Figure 2-10). These pins can be switched
from regular DIO to implement an I2C interface by setting the I/O RAM register DIO_EEX (0x2008[4]) to 1.
Pull-up resistors of 3k
Ω
must be provided for both the SCL and SDA signals.
Figure 2-10: EEPROM Circuit
2.3.4 CONNECTING THREE-WIRE EEPROMS
µWire EEPROMs and other compatible devices should be connected to the DIO pins DIO4 and DIO5, as
shown in Figure 2-11. DIO5 connects to both the DI and DO pins of the three-wire device. The CS pin must
be connected to a vacant DIO pin of the 71M6521. A pull-up resistor of roughly 3k
Ω
to V3P3 should be used
for the DI/DO signals, and the CS pin should be pulled down with a resistor to prevent that the three-wire
device is selected on power-up, before the 71M6521 can establish a stable signal for CS. The
DIO_EEX
register in I/O RAM must be set to 10 in order to convert the DIO pins DIO4 and DIO5 to uWire pins. The
pull-up resistor for DIO5 may not be necessary.
Figure 2-11: Three-Wire EEPROM Circuit
2.3.5 LCD
The 71M6521 has an on-chip LCD controller capable of controlling static or multiplexed LCDs. Figure 2-12
shows the basic connection for LCDs. Note that the LCD module itself has no power connection.
DIO4
DIO5
6521
RTC
SCL
SDA
V3P3
3k
Ω
DIO4
DIO5
6521
RTC
SCL
SDA
V3P3
3k
Ω
DIO4
DIO5
6521
EEPROM
SCLK
DI
V3P3D
3k
Ω
*
CS
DIOn
DO
3k
Ω
3k
Ω
DIO4
DIO5
6521
EEPROM
SCLK
DI
V3P3D
3k
Ω
*
CS
DIOn
DO
3k
Ω
3k
Ω