ADF7021 datasheet(41/64 Pages) AD

41 / 64 page

Data Sheet

ADF7021

Rev. B | Page 41 of 64

PACKET STRUCTURE AND CODING

The suggested packet structure to use with the ADF7021 is

shown in Figure 53.

PREAMBLE

SYNC

WORD

FIELD

DATA FIELD

CRC

Figure 53. Typical Format of a Transmit Protocol

Refer to the Receiver Setup section for information on the

required preamble structure and length for the various modulation

schemes.

PROGRAMMING AFTER INITIAL POWER-UP

Table 22 lists the minimum number of writes needed to set up

the ADF7021 in either Tx or Rx mode after CE is brought high.

Additional registers can also be written to tailor the part to a

particular application, such as setting up sync byte detection or

enabling AFC. When going from Tx to Rx or vice versa, the

user needs to toggle the Tx/Rx bit and write only to Register 0

to alter the LO by 100 kHz.

Table 22. Minimum Register Writes Required for Tx/Rx Setup

Mode

Registers

Reg 1

Reg 3

Reg 0

Reg 2

Reg 1

Reg 3

Reg 0

Reg 5

Reg 4

Tx to Rx and Rx to Tx

Reg 0

The recommended programming sequences for transmit and

receive are shown in Figure 54 and Figure 55, respectively. The

difference in the power-up routine for a TCXO and XTAL

reference is shown in these figures.

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