2 frame control field (fcf), Atmega128rfa1 – Rainbow Electronics ATmega128RFA1 User Manual
Page 63
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8266A-MCU Wireless-12/09
ATmega128RFA1
9.5.1.2.2 Frame Control Field (FCF)
The FCF consists of 16 bits, and occupies the first two octets of either the MPDU or the
PSDU, respectively.
Figure 9-26. IEEE 802.15.4-2006 Frame Control Field (FCF)
Bit [2:0]: describe the frame type.
summarizes frame types defined
by IEEE 802.15.4, section 7.2.1.1.1.
Table 9-16. Frame Control Field – Frame Type Subfield
Frame Control Field Bit Assignments
Frame Type Value
b
2
b
1
b
0
Value
Description
000
0
Beacon
001
1
Data
010
2
Acknowledge
011
3
MAC command
100 – 111
4 – 7
Reserved
This subfield is used for address filtering by the third level filter rules. Only frame types
0 – 3 pass the third level filter rules (refer to section
).
Automatic address filtering of the radio transceiver is enabled when using the
RX_AACK mode (refer to
"RX_AACK_ON – Receive with Automatic ACK" on page 46
).
A reserved frame (frame type value > 3) can be received if bit AACK_UPLD_RES_FT of
register XAH_CTRL_1 is set. For details refer to chapter
802.15.4 Compliant Scenarios" on page 52
. Address filtering is also provided in Basic
Operating Mode as explained in
"Basic Operating Mode" on page 35
.
Bit 3: indicates whether security processing applies to this frame.
Bit 4: is the “Frame Pending” subfield. This field can be set in an acknowledgment
frame (ACK) in response to a data request MAC command frame. This bit indicates that
the node, which transmitted the ACK, has more data to send to the node receiving the
ACK.
For acknowledgment frames automatically generated by the radio transceiver, this bit is
set according to the content of bit AACK_SET_PD of register CSMA_SEED_1 if the
received frame was a data request MAC command frame.
Bit 5: forms the “Acknowledgment Request” subfield. If this bit is set within a data or
MAC command frame that is not broadcast, the recipient shall acknowledge the
reception of the frame within the time specified by IEEE 802.15.4 (i.e. within 192 µs for
non beacon-enabled networks).
The radio transceiver parses this bit during RX_AACK mode and transmits an
acknowledgment frame if necessary.
In TX_ARET mode this bit indicates if an acknowledgement frame is expected after
transmitting a frame. If this is the case, the receiver waits for the acknowledgment
frame, otherwise the TX_ARET transaction is finished.