71M6521DE Datasheet, PDF (69/107 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521DE/DH/FE Data Sheet
Connecting Three-Wire EEPROMs
µWire EEPROMs and other compatible devices should be connected to the DIO pins DIO4 and DIO5, as shown in
Figure 36. 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 71M6521DE/DH/FE. A pull-up resistor of roughly 10kΩ to V3P3D (to ensure operation in
BROWNOUT mode) 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 71M6521DE/DH/FE 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
MICROWIRE pins. The pull-up resistor for DIO5 may not be necessary.
71M6521
10kΩ
DIO4
DIO5
DIOn
V3P3D
10kΩ
EEPROM
SCLK
DI
DO
CS
Figure 36: Three-Wire EEPROM Connection
UART0 (TX/RX)
The RX pin should be pulled down by a 10kΩ resistor and additionally protected by a 100pF ceramic capacitor, as
shown in Figure 37.
71M6521E
100pF 10kΩ
RX
RX
TX
TX
Figure 37: Connections for the RX Pin
Rev 2
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