User Manual

66
8111A–AVR–05/08
AT86RF231
Note that if no ACK is expected (according to the content of the received frame in the Frame
Buffer), the radio transceiver issues IRQ_3 (TRX_END) directly after the frame transmission has
been completed. The value of register bits TRAC_STATUS (register 0x02, TRX_STATE) is set
to SUCCESS.
A value of MAX_CSMA_RETRIES = 7 initiates an immediate TX_ARET transaction without per-
forming CSMA-CA. This is required to support slotted acknowledgement operation. Further the
value MAX_FRAME_RETRIES is ignored and the TX_ARET transaction is performed only once.
A timing example of a TX_ARET transaction is shown in Figure 7-13 on page 66.
Figure 7-13. Example Timing of a TX_ARET Transaction
Note: t
CSMA-CA
defines the random CSMA-CA processing time
Here an example data frame of length 10 with an ACK request is transmitted, see Table 7-13 on
page 67. After that the AT86RF231 switches to receive mode and expects an acknowledgement
response. During the whole transaction including frame transmit, wait for ACK and ACK receive
the radio transceiver status register TRX_STATUS (register 0x01, TRX_STATUS) signals
BUSY_TX_ARET.
A successful reception of the acknowledgment frame is indicated by IRQ_3 (TRX_END). The
status register TRX_STATUS (register 0x01, TRX_STATUS) changes back to TX_ARET_ON.
The TX_ARET status register TRAC_STATUS changes as well to TRAC_STATUS = SUCCESS
Table 7-12. Interpretation of TRAC_STATUS register bits
Value Name Description
0
SUCCESS The transaction was responded by a valid ACK, or, if no
ACK is requested, after a successful frame transmission
1 SUCCESS_DATA_PENDING Equivalent to SUCCESS, indicates pending frame data
according to the MHR frame control field of the received
ACK response
3 CHANNEL_ACCESS_FAILURE Channel is still busy after MAX_CSMA_RETRIES of
CSMA-CA
5 NO_ACK No acknowledgement frames were received during all retry
attempts
7 INVALID Entering TX_ARET mode sets TRAC_STATUS = 7
RX/TX
Frame
on Air
TX_ARET_ON BUSY_TX_ARET
TRX_STATE
FrameType
TX_ARET_ON
RX/TX
RX
TRX_END
IRQ
Typ. Processing Delay
16 µs
6720x
time [µs]
128
x+352
SLP_TR
TX
t
IRQ
Data Frame (Length = 10, ACK=1) ACK Frame
32 µst
CSMA-CA
TXCSMA-CA
RX