NRF52811-QCAA-R datasheet(194/444 Pages) NORDIC

194 / 444 page

Peripherals

For AoA RX mode, the sample spacing after the reference period is determined by

DFECTRL1.TSWITCHSPACING, as listed in the table below.

DFECTRL1.TSWITCHSPACING

Sample spacing

2 µs

CTEINLINECONF.CTEINLINERXMODE1US

4 µs

CTEINLINECONF.CTEINLINERXMODE2US

Other

DFECTRL1.TSAMPLESPACING

Table 66: Sample spacing when CTEINLINECONF.CTEINLINECTRLEN is set and the device is in AoA RX mode

For the reference- and switching periods, DFECTRL1.TSAMPLESPACINGREF and

DFECTRL1.TSAMPLESPACING can be used to achieve oversampling.

6.14.13 IEEE 802.15.4 operation

With the MODE=Ieee802154_250kbit the RADIO will comply with the IEEE 802.15.4-2006 standard

implementing its 250 kbps, 2450 MHz, O-QPSK PHY.

The IEEE 802.15.4 standard differs from Nordic's proprietary and Bluetooth® low energy modes. Notable

differences include modulation scheme, channel structure, packet structure, security, and medium access

control.

The main features of the IEEE 802.15.4 mode are:

• Ultra-low power 250 kbps, 2450 MHz, IEEE 802.15.4-2006 compliant link

• Clear channel assessment

• Energy detection scan

• CRC generation

6.14.13.1 Packet structure

The IEEE 802.15.4 standard defines an on-the-air frame/packet that is different from what is used in BLE

mode.

The following figure provides an overview of the physical frame structure and its timing.

PHY protocol data unit (PPDU)

Preamble sequence

SFD

Length

PHY payload

5 octets synchronization header (SHR)

1 octet

(PHR)

Maximum 127 octets (PSDU)

160 µs

32 µs

<=4064 µs

MAC protocol data unit (MPDU)

Figure 77: IEEE 802.15.4 frame format (PPDU)

The standard uses the term octet for an 8-bit storage unit within the PPDU. For timing, the value symbol is

used, and it has a duration of 16 µs.

The total usable payload (PSDU) is 127 octets, but when CRC is in use, this is reduced to 125 octets of

usable payload.

The preamble sequence consists of four octets that are all zero, and are used for synchronizing the

RADIO's receiver. Following the preamble is the single octet start of frame delimiter (SFD), with a fixed

value of 0xA7. An alternate SFD can be programmed through the SFD register, providing an initial level of

frame filtering for those who choose non-standard compliance. It is a valuable feature when operating in

a congested or private network. The preamble sequence and the SFD are generated by the RADIO, and are

not programmed by the user into the frame buffer.

4454_140 v1.0

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