CC2520_12 Datasheet, PDF (73/133 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
20 Receive Mode
This section describes how to control the receiver, integrated RX frame processing, and how use the RX
FIFO.
20.1 RX Control
The CC2520 receiver is turned on and off with the SRXON and SRFOFF command strobes, and with the
RXENABLE registers. The command strobes provide a "hard" on/off mechanism, while RXENABLE
manipulation provides a "soft" on/off mechanism.
The receiver will be turned on by the following actions:
• The SRXON strobe:
o Sets RXENABLE[15]
o Aborts ongoing transmission/reception by forcing a transition to RX calibration.
• The STXON strobe when FRMCTRL1.SET_RXENMASK_ON_TX is enabled:
o Sets RXENABLE[14]
o The receiver is enabled after transmission completes.
• Setting RXENABLE != 0x0000:
o Does not abort ongoing transmission/reception.
The receiver will be turned off by the following actions:
• The SRFOFF strobe:
o Clears RXENABLE[15:0]
o Aborts ongoing transmission/reception by forcing the transition to IDLE mode.
• Setting RXENABLE = 0x0000
o Does not abort ongoing transmission/reception. Once the ongoing transmission/reception is
finished, the CC2520 will return to IDLE state.
There are several ways to manipulate the RXENABLE registers:
• The REGWR and MEMWR instructions
• The BSET and BCLR instructions
• The RXENABLEAND and RXENABLEOR instructions
• The SRXMASKBITSET and SRXMASKBITCLR strobes (affecting RXENABLE[13])
• The SRXON, SRFOFF and STXON strobes, including the FRMCTRL1.SET_RXMASK_ON_TX
setting
20.2 RX State Timing
The receiver is ready 192 us after RX has been enabled by one of the methods described above. This is
referred to as "RX turnaround time" in [2].
When returning to receive mode after frame reception, there is by default an interval of 192 us where SFD
detection is disabled. This interval can be disabled by clearing FSMCTRL.RX2RX_TIME_OFF.
20.3 Frame Processing
CC2520 integrates critical portions of the RX requirements in IEEE 802.15.4-2003 and -2006 in hardware.
This reduces the microcontroller interruption rate, simplifies the software that handles frame reception, and
provides the results with minimum latency.
During reception of a single frame, the CC2520 performs the following frame processing steps:
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