The Extended Operating Mode is a hardware MAC accelerator and goes beyond the
basic radio transceiver functionality provided by the Basic Operating Mode. It handles
time critical MAC tasks requested by the IEEE 802.15.4 standard or by hardware such
as automatic acknowledgement, automatic CSMA-CA and retransmission. This results
in a more efficient IEEE 802.15.4 software MAC implementation including reduced code
size and may allow operating at lower microcontroller clock rates.

The Extended Operating Mode is designed to support IEEE 802.15.4-2006 compliant
frames; the mode is backward compatible to IEEE 802.15.4-2003 and supports non
IEEE 802.15.4 compliant frames. This mode comprises the following procedures:

Automatic acknowledgement (RX_AACK) divides into the tasks:

•

Frame reception and automatic FCS check;

•

Configurable addressing fields check;

•

Interrupt indicating address match;

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Interrupt indicating frame reception, if it passes address filtering and FCS check;

•

Automatic ACK frame transmission (if the received frame passed the address filter

and FCS check and if an ACK is required by the frame type and ACK request);

•

Support of slotted acknowledgment using SLPTR bit for frame start.

Automatic CSMA-CA and Retransmission (TX_ARET) divides into the tasks:

•

CSMA-CA including automatic CCA retry and random back-off;

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Frame transmission and automatic FCS field generation;

•

Reception of ACK frame (if an ACK was requested);

•

Automatic frame retry if ACK was expected but not received;

•

Interrupt signaling with transaction status.

Automatic FCS check and generation (refer to

"Frame Check Sequence (FCS)" on

page 66)

is used by the RX_AACK and TX_ARET modes. In RX_AACK mode an

automatic FCS check is always performed for incoming frames.

An ACK received in TX_ARET mode within the time required by IEEE 802.15.4 is
accepted if the FCS is valid and if the sequence number of the ACK matches the
sequence number of the previously transmitted frame. Dependent on the value of the