14.4.1.4.3 High Data Rate Mode Options

Reduced Acknowledgment Time

If the AACK_ACK_TIME bit in the XAM_CTRL_1 register (XAH_CTRL_1.AACK_ACK_TIME) is set, the acknowledgment time is reduced to the duration of two symbol periods for 200 and 400kb/s data rates, and to three symbol periods for 500 and 1000kb/s data rates. The reduced acknowledgment time is untouched in IEEE 802.15.4. Otherwise, it defaults to 12 symbol periods according to IEEE 802.15.4.

Receiver Sensitivity Control

The different data rates between PPDU header (SHR and PHR) and PHY payload (PSDU) cause a different sensitivity between header and payload. This can be adjusted by defining sensitivity threshold levels of the receiver. With a sensitivity threshold level set, the AT86RF212B does not synchronize to frames with an RSSI level below that threshold. The sensitivity threshold is configured by the RX_PDT_LEVEL bits in the RX_SYN register (RX_SYN.RX_PDT_LEVEL).

Scrambler

For data rates 400kb/s and 1000kb/s, additional chip scrambling is applied per default in order to mitigate data dependent spectral properties. Scrambling can be disabled if the OQPSK_SCRAM_EN bit in the TRX_CTRL_2 register (TRX_CTRL_2.OQPSK_SCRAM_EN) is set to zero.

Energy Detection

The Energy Detection (ED) measurement time span is eight symbol periods according to IEEE 802.15.4. For frames operated at a higher data rate, the automated measurement duration is reduced to two symbol periods taking reduced frame durations into account. This means, the ED measurement time is 80µs for modes 200kb/s and 400kb/s, and 32µs for modes 500kb/s and 1000kb/s. For manually initiated ED measurements in these modes, the measurement time is still eight symbol periods.

Carrier Sense

For clear channel assessment, IEEE 802.15.4-2006 specifies several modes which may either apply “energy above threshold” or “carrier sense” (CS) or a combination of both. Since signals of the High Data Rate Modes are not compliant to IEEE 802.15.4-2006, CS is not supported when the AT86RF212B is operating in these modes. However, “energy above threshold” is supported.

Link Quality Indicator (LQI)

For the High Data Rate Modes, the link quality value does not contain useful information and should be discarded.