CC2430
Radio : Receive mode
event that causes a RADIO DMA trigger, is
when data is read from the RXFIFO (through
RFD SFR register) and there is still more data
available in the RXFIFO.
14.7 Receive mode
In receive mode, the interrupt flag
RFIF.IRQ_SFD goes high and the RF
interrupt is requested after the start of frame
delimiter (SFD) field has been completely
received. If address recognition is disabled or
is successful, the RFSTATUS.SFDbit goes low
again only after the last byte of the MPDU has
been received. If the received frame fails
address recognition, the RFSTATUS.SFD bit
goes low immediately. This is illustrated in
Figure 35.
number of bytes in the RXFIFO exceeds the
programmed threshold.
The RFSTATUS.FIFOP bit will also go high
when the last byte of a new packet is received,
even if the threshold is not exceeded. If so the
RFSTATUS.FIFOPbit will go back to low once
one byte has been read out of the RXFIFO.
When address recognition is enabled, data
should not be read out of the RXFIFO before
the address is completely received, since the
frame may be automatically flushed by CC2430
if it fails address recognition. This may be
handled by using the RFSTATUS.FIFOP bit,
since this bit does not go high until the frame
passes address recognition.
The RFSTATUS.FIFObit is high when there is
one or more data bytes in the RXFIFO. The
first byte to be stored in the RXFIFO is the
length field of the received frame, i.e. the
RFSTATUS.FIFO bit is set high when the
length field is written to the RXFIFO. The
RFSTATUS.FIFO bit then remains high until
the RXFIFO is empty. The RF register
RXFIFOCNT contains the number of bytes
present in the RXFIFO.
Figure 36 shows an example of status bit
activity when reading a packet from the
RXFIFO. In this example, the packet size is 8
bytes, IOCFG0.FIFOP_THR
=
3
and
MDMCTRL0L.AUTOCRC is set. The length will
be 8 bytes, RSSI will contain the average
RSSI level during receiving of the packet and
FCS/corr contains information of FCS check
result and the correlation levels.
The RFSTATUS.FIFOP bit is high when the
number of unread bytes in the RXFIFO
exceeds the threshold programmed into
IOCFG0.FIFOP_THR.
When
address
recognition is enabled the RFSTATUS.FIFOP
bit will not go high until the incoming frame
passes address recognition, even if the
14.8 RXFIFO overflow
The RXFIFO can only contain a maximum of
128 bytes at a given time. This may be divided
between multiple frames, as long as the total
number of bytes is 128 or less. If an overflow
occurs in the RXFIFO, this is signaled to the
CPU by asserting the RFERR interrupt when
enabled. In addition the radio will set
the RXFIFO will not be affected by the
overflow, i.e. frames already received may be
read out.
A SFLUSHRXcommand strobe is required after
a RXFIFO overflow to enable reception of new
data.
RFSTATUS.FIFO
bit
low
while
the
RFSTATUS.FIFOP bit is high. Data already in
CC2430 Data Sheet (rev. 2.1) SWRS036F
Page 158 of 211
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