ZAURA Datasheet, PDF (19/99 Pages) –

ZAURA RF Wireless Library
Programmer’s Reference Manual
7
DA Frame Format
The simplest of the ZAURA RF Wireless frame formats is DA. Fields
within the DA frame are depicted in Figure 1.
PA(2) NID(1–4) Len(1)
DA(1) Data(58) CRC(2)
Figure 1. Fields within the DA Frame
Fields shown in white are configured by the ZAURA RF Wireless Library
and cannot be modified by the user. The preamble (PA) is a fixed pattern
of repeating 1010 bits (0xAA). The radio hardware uses the preamble for
synchronizing the receiver’s clock to the transmitter’s clock. The ZAURA
RF Library is configured to transmit two preamble bytes, but the radio
will typically emit an extra PA as it prepares for transmission.
The CRC is calculated over the Len, DA and Data fields. The ZAURA RF
Wireless Module configures the radio hardware to automatically generate
the CRC on transmission and validate the CRC upon packet reception.
The ZAURA Module only processes frames with a valid CRC; the radio
hardware automatically rejects frames with an invalid CRC.
The ZAURA Module configures the radio to only accept packets that
match the user-configurable Network ID (NID). The NID can be between
1 and 4 bytes. The longer the NID, the less susceptible the receiver will be
to noise at a cost of a lower effective data rate. Zilog recommends using a
NID of at least 2 bytes; this NID should not contain long sequences of
repeated binary 1 or 0 digits.
The length field (Len) contains the number of bytes in the Data field.
Note that the Len fields of the RF frames include the number of bytes
between the Len field and the CRC. The ZAURA RF Wireless Library
automatically adjusts the length field of received and transmitted packets
RM006003-1011
Frame Formats