Rainbow Electronics ATmega128RFA1 User Manual
Page 47
47
8266A-MCU Wireless-12/09
ATmega128RFA1
Generally, at nodes, configured as a normal device or PAN coordinator, a frame is not
indicated if the frame filter does not match and the FCS is invalid. Otherwise, the
TRX_24_RX_END interrupt is issued after the completion of the frame reception. The
microcontroller can then read the frame. An exception applies if promiscuous mode is
enabled (see section
"Configuration of IEEE Scenarios" on
page 50). In that case a
TRX_24_RX_END interrupt is issued even if the FCS fails.
If the content of the MAC addressing fields of the received frame (refer to
IEEE 802.15.4 section 7.2.1) matches one of the configured addresses, dependent on
the addressing mode, an address match interrupt (TRX24_XAH_AMI) is issued (refer to
section
page 54). The expected address values are to be stored in
registers Short-address, PAN-ID and IEEE-address. Frame filtering as described in
section
page 54 is also valid for Basic Operating Mode.
During reception the radio transceiver parses bit[5] (ACK Request) of the frame control
field of the received data or the MAC command frame to check if an ACK reply is
expected. In that case and if the frame passes the third level of filtering (see
IEEE 802.15.4-2006, section 7.5.6.2), the radio transceiver automatically generates and
transmits an ACK frame. After the ACK transmission is finished, a TRX24_TX_END
interrupt is generated.
The content of the frame pending subfield of the ACK response is set by bit
AACK_SET_PD of register CSMA_SEED_1 when the ACK frame is sent in response to
a data request MAC command frame, otherwise this subfield is set to “0”. The
sequence number is copied from the received frame.
Optionally, the start of the transmission of the acknowledgement frame can be
influenced by register bit AACK_ACK_TIME. Default value (according to standard
IEEE 802.15.4, page 54) is 12 symbol times after the reception of the last symbol of a
data or MAC command frame.
If the bit AACK_DIS_ACK of register CSMA_SEED_1 is set, no acknowledgement
frame is sent even if an acknowledgment frame was requested. This is useful for
operating the MAC hardware accelerator in promiscuous mode (see section
"Configuration of non IEEE 802.15.4 Compliant Scenarios" on
page 52).
The status of the RX_AACK operation is indicated by the bits TRAC_STATUS of
register TRAC_STATUS.
During the operations described above the radio transceiver remains in
BUSY_RX_AACK state.