Texas Instruments CC2650DK 사용자 설명서
IEEE 802.15.4
When a frame has been received, the RSSI observed while receiving the frame is written to pOutput-
>lastRssi. If the frame was a beacon frame accepted by the frame filtering and with CRC OK, the
timestamp at the beginning of the frame is written to pOutput ->beaconTimeStamp. If the timestamp is
appended to the RX entry element, see
>lastRssi. If the frame was a beacon frame accepted by the frame filtering and with CRC OK, the
timestamp at the beginning of the frame is written to pOutput ->beaconTimeStamp. If the timestamp is
appended to the RX entry element, see
, Receive Buffers, these two timestamps are the
same for a beacon frame.
After a packet has been received, the radio CPU either restarts sync search or sends an acknowledgment
frame. The conditions for the latter are as given in
frame. The conditions for the latter are as given in
, ACK Transmission.
23.5.4.1.3 ACK Transmission
After a packet has been received, the radio CPU initiates transmission of an acknowledgment frame,
given that all of the conditions listed below are satisfied:
given that all of the conditions listed below are satisfied:
•
Auto ACK is enabled by frameFiltOpt.autoAckEn = 1.
•
The frame was accepted by frame filtering (bIgnore = 0)
•
The frame was a data frame or a MAC command frame
•
The destination address was not the broadcast address
•
The ACK request bit of the FCF was set
•
The CRC check passed (bCrcErr = 0)
•
The frame fit in the receive queue
The transmit time of the ACK packet is timed by the radio CPU, depending on frameFiltOpt.slottedAckEn.
If this bit is 0, the ACK packet is transmitted aTurnaroundTime symbol periods, or 192 µs, after the end of
the received packet. Otherwise, slotted ACK is used. Assume that the received packet started on a
backoff-slot boundary. The ACK frame then starts a whole number of backoff periods later than the start of
the received frame, at the first backoff boundary following at least one TurnaroundTime-symbol period
after the end of the received frame.
If this bit is 0, the ACK packet is transmitted aTurnaroundTime symbol periods, or 192 µs, after the end of
the received packet. Otherwise, slotted ACK is used. Assume that the received packet started on a
backoff-slot boundary. The ACK frame then starts a whole number of backoff periods later than the start of
the received frame, at the first backoff boundary following at least one TurnaroundTime-symbol period
after the end of the received frame.
The contents of the automatically-transmitted ACK frame are as follows:
•
The PHY header is 0x05
•
The PHY payload consists of a 3-byte MAC header and a 2-byte MAC footer
•
The MAC header starts with the 2-byte FCF with the following fields:
–
The Frame Type subfield is 010b
–
The Frame Pending subfield is set as described in
, Source Matching
–
The remaining subfields are set to all zeros
•
The next byte in the MAC header is the sequence number, whichis set equal to the sequence number
of the received frame
of the received frame
•
The MAC footer is the FCS, which is calculated automatically
After the ACK frame has been transmitted, a TX_ACK interrupt is raised. The radio CPU then enables the
receiver again.
receiver again.
23.5.4.1.4 End of Receive Operation
The receive operation can end as a result of the end trigger given by endTrigger and endTime, or by a
command. The commands that can end the receive operation are the immediate commands
CMD_ABORT and CMD_STOP, and the foreground-level radio operation command
CMD_IEEE_ABORT_BG. The end-trigger and the CMD_STOP command cause the receiver to keep
running until the end of the frame, or until the reception would otherwise be stopped if observed while a
packet was being received. The CMD_ABORT and CMD_IEEE_ABORT_BG commands cause the
receiver to stop as quickly as the implementation allows.
command. The commands that can end the receive operation are the immediate commands
CMD_ABORT and CMD_STOP, and the foreground-level radio operation command
CMD_IEEE_ABORT_BG. The end-trigger and the CMD_STOP command cause the receiver to keep
running until the end of the frame, or until the reception would otherwise be stopped if observed while a
packet was being received. The CMD_ABORT and CMD_IEEE_ABORT_BG commands cause the
receiver to stop as quickly as the implementation allows.
A receive operation ends through one of the causes listed in
. The status field of the command
structure after the command has ended indicates the reason why the operation ended. In all cases, a
COMMAND_DONE interrupt is raised. In each case, the result is indicated as True, False, or Abort. This
decides whether to start the next command (if any) indicated in pNextOp, or to return to an idle state.
Before the receive operation ends, the radio CPU writes the maximum observed RSSI during the receive
operation to pOutput->maxRssi.
COMMAND_DONE interrupt is raised. In each case, the result is indicated as True, False, or Abort. This
decides whether to start the next command (if any) indicated in pNextOp, or to return to an idle state.
Before the receive operation ends, the radio CPU writes the maximum observed RSSI during the receive
operation to pOutput->maxRssi.
1506
Radio
SWCU117A – February 2015 – Revised March 2015
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