CC2520_11 Datasheet, PDF (85/133 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
21 Radio Control State Machine
The FSM module is responsible for maintaining the TX FIFO and RX FIFO pointers, control of analog
“dynamic” signals such as power up / power down, control of the data flow within the RF core, generation of
automatic acknowledgement frames and control of all analog RF calibration.
rxenable ^{= 0}
rxenable != 0
idle
0
SRFOFF and
tx_active=’0'
all states
STXON
SFLUSHRX
RX
calibration
2
Timeout
192 µs
SFD wait
3-6
SRXON _{or SFLUSHRX}
any RX state
Timeout 190 µs
RX/RX wait
14
SFD detected
Framneocaocmkpslectheeddaunledd
RX
7-13
RXFIFO
reset
16
Frame not for me
Overflow
RX overflow
17
Slotted ACK
Unslotted ACK
TX/RX transit
40
STXONCCA and cca=’1'
TX
calibration
32
Timeout
192 µs
TX underflow
56
Underflow
Timeout 2 µs
TX
34-38
Frame sent
rxenable! = 0
TX final
39
TX shutdown
26, 57
rxenable = 0
SRFOFF or
SRXON
ACK delay
55
Timeout X µs
(depending on length byte of
the received frame)
ACK
calibration
48
Timeour 192 µs
ACK
49-54
all TX and
ACK states
Figure 30: Main FSM
Table 18 shows the mapping from FSM state to the number which can be read from the FSMSTAT0
register. Note that although it is possible to read the state of the FSM, this information should not be used to
control the program flow in the application software. The states may change very quickly (every 32 MHz
clock cycle) and an 8 MHz SPI is not able to capture all the activities.
Table 18: FSM State Mapping
State name
Idle
RX calibration
SFD wait
RX
RX/RX wait
RXFIFO reset
RX overflow
State number Number
decimal
hex
tx_active rx_active
0
0x00
0
0
2
0x02
0
1
3-6
0x03 – 0x06 0
1
7 - 13
0x07 – 0x0D 0
1
14
0x0E
0
1
16
0x10
0
1
17
0x11
0
0
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