2 extended operating mode, Section 7.2 “extended operating mode, Ed in – Rainbow Electronics AT86RF231 User Manual
Page 47: Section 7.2 “extended operating mode” on, Section 7.2 “extended
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8111A–AVR–05/08
AT86RF231
7.2
Extended Operating Mode
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, by hardware, such as automatic acknowledge-
ment, 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 the use of a smaller
microcontroller or to operate at low 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 com-
pliant 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
• 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 SLP_TR pin
Automatic CSMA-CA and Retransmission (TX_ARET) divides into the tasks:
• CSMA-CA including automatic CCA retry and random back-off
• 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
Section 8.2 “Frame Check Sequence (FCS)” on
, is used by the RX_AACK and TX_ARET modes. In RX_AACK mode, an automatic
FCS check is always performed for incoming frames.
In TX_ARET mode, an ACK, received 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 frame pending subfield in the
received acknowledgement frame the transaction status is set, see
.
An AT86RF231 state diagram including the Extended Operating Mode states is shown in
. Yellow marked states represent the Basic Operating Mode; blue marked states
represent the Extended Operating Mode.