The TX_ADDR register is used to set the destination address for the packets that will be transmitted.
This table is copied from the nRF24L01 product specification (page 56).
|TX_ADDR||39:0||0xE7E7E7E7E7||R/W||Transmit address. Used for a PTX device only. (LSByte is written first) Set RX_ADDR_P0 equal to this address to handle automatic acknowledge if this is a PTX device with Enhanced ShockBurst™ enabled.|
See the comments to the RX_ADDR_Pn Registers for a discussion on addresses.