Product Specs

Table Of Contents
23 RADIO 2.4 GHz Radio
Page
206
1 0 1 0 1 0 1 0 1
0 1 0 1 0 1 0 1 0
PREAMBLE
BASE
PREFIX
S0 LENGTH S1
PAYLOAD
CRC
LSByte MSByte
S0
LENGTH
S1
PAYLOAD
LSByte
ADDRESS
In addition, the S0INCL field in PCNF0 determines if S0 is present in RAM at all if its length is zero. If
present, one byte is allocated in RAM.
The size of S0 is configured through the S0LEN field in PCNF0. The size of LENGTH is configured through
the LFLEN field in PCNF0. The size of S1 is configured through the S1LEN field in PCNF0. The size of the
payload is configured through the value in RAM corresponding to the LENGTH field. The size of the static
add-on to the payload is configured through the STATLEN field in PCNF1.
The MAXLEN field in the PCNF1 register configures the maximum packet payload plus add-on size in
number of bytes that can be transmitted or received by the RADIO. This feature can be used to ensure that
the RADIO does not overwrite, or read beyond, the RAM assigned to the packet payload. This means that
if the packet payload length defined by PCNF1.STATLEN and the LENGTH field in the packet specifies a
packet larger than MAXLEN, the payload will be truncated at MAXLEN.
Note that MAXLEN includes the payload and the add-on, but excludes the size occupied by the S0, LENGTH
and S1 fields. This has to be taken into account when allocating RAM.
If the payload plus add-on length is specified larger than MAXLEN, the RADIO will still transmit or receive in
the same way as before except the payload is now truncated to MAXLEN. The packet's LENGTH field will
not be altered when the payload is truncated. The RADIO will calculate CRC as if the packet length is equal
to MAXLEN.
If the PACKETPTR is not pointing to the Data RAM region, an EasyDMA transfer may result in a HardFault
or RAM corruption. See Memory on page 23 for more information about the different memory regions.
The DISABLED event indicates that the EasyDMA has finished accessing the RAM.
23.2 Packet configuration
A Radio packet contains the following fields: PREAMBLE, ADDRESS, S0, LENGTH, S1, PAYLOAD and
CRC.
See Figure 30: On-air packet layout on page 206. Not shown in the figure is the static payload add-on (the
length of which is defined in STATLEN, and which is 0 bytes long in a standard BLE packet), and would be
sent between PAYLOAD and CRC. The Radio sends the different fields in the packet in the order they are
illustrated below, from left to right. The preamble will be sent least significant bit first on-air.
0x55
0xAA
Figure 30: On-air packet layout
For all modes, except for 2 Mbit/s Bluetooth Low Energy mode, the preamble is one byte long. For 2 Mbit/s
Bluetooth Low Energy mode the preamble is 2 bytes long. If the first bit of the ADDRESS is 0 the preamble
will be set to 0xAA otherwise the PREAMBLE will be set to 0x55.
Radio packets are stored in memory inside instances of a radio packet data structure as illustrated in
Figure 31: In-RAM representation of radio packet, S0, LENGTH and S1 are optional on page 206. The
PREAMBLE, ADDRESS and CRC fields are omitted in this data structure.
0 LSByte n
Figure 31: In-RAM representation of radio packet, S0, LENGTH and S1 are optional
LSBit
LSBit
LSBit
MSBit