MRF24J40_08 Datasheet, PDF (108/152 Pages) Microchip Technology – IEEE 802.15.4™ 2.4 GHz RF Transceiver

MRF24J40
3.12 Transmission
IEEE 802.15.4 Standard defines four frame types:
Acknowledgment, Data, Beacon and MAC Command
frame. The transmission of the Acknowledgment frame
is handled automatically in hardware by the MRF24J40
and is covered in Section 3.13 “Acknowledgement”.
Hardware management of the transmission of data,
beacon and MAC command frames are handled in four
transmit (TX) FIFOs.
Each TX FIFO has a specific purpose depending on if the
MRF24J40 is configured for Beacon or Non-
beacon-Enabled mode. Configuring the MRF24J40 for
beacon-enabled network operation is covered in
Section 3.8.1 “Beacon-Enabled Network”. Configuring
the MRF24J40 for nonbeacon-enabled network operation
is covered in Section 3.8.2 “Nonbeacon-Enabled
Network”.
The four TX FIFOs are:
TX Normal FIFO – Used for the transmission of data
and MAC command frames during the Contention
Access Phase (CAP) of the superframe if the device is
operating in Beacon-Enabled mode and for all
transmissions when the device is operating in
Nonbeacon-Enabled mode.
TX Beacon FIFO – Used for the transmission of the
beacon frames.
TX GTS1 FIFO and TX GTS2 FIFO – Used for the
transmission of data during the Contention Free Period
(CFP) of the superframe if the device is operating
in Beacon-Enabled mode. Refer to Section 3.8.1
“Beacon-Enabled Network” for more information
about guaranteed time slots in Beacon-Enabled mode.
Figure 3-10 summarizes the memory map for each of
the TX FIFOs. Each TX FIFO occupies 128 bytes of
memory and can hold one frame at a time.
Figure 3-11 shows the flow of data from the TX FIFO to
on air packet and summarizes the data, beacon and
MAC command frames.
FIGURE 3-10:
MEMORY MAP OF TX
FIFOS
0x000
0x07F
0x080
0x0FF
0x100
0x17F
0x180
0x1FF
Long Address
Memory Space
TX Normal FIFO
128 bytes
TX Beacon FIFO
128 bytes
TX GTS1 FIFO
128 bytes
TX GTS2 FIFO
128 bytes
DS39776B-page 106
Preliminary
© 2008 Microchip Technology Inc.