Question
On page 46 of datasheet, when ADF7021 communicates with SCM and use Standard
Transmit/Receive Data Interface mode, there is a diode in MISO port, what is it
used for?
Answer
This diode is used for unidirection protection.
1）ADuC Receive mode： in this mode,ADF7021 TxRxDATA pin send data to ADuC84x
MOSI pin.MISO must keep high to cut off diode to make sure MISO data does not
interrupt TxRxData.
2）ADuC Transmit mode： in this mode, ADF7021 xRxData pin receive ADuC84x
data.there is a pull up in TxRxData pin, when MISO send 0, diode current flows
and 0 is sent to TxRxData, if sending 1, diode cut off and pull up takes
TxRxData pin to high and realize input 1.