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Preamble
SFD
MHR
FCS
LEN
(1)
(5)
(4)
(3)
(2)
MAC Payload
Preamble
SFD
MHR
FCS
LEN
Transmitted Acknowledgment Frame
Received Frame
M0110-02
Receive Mode
–
Sets
RXENABLE[7]
–
Aborts ongoing transmission/reception by forcing a transition to RX calibration.
•
The STXON strobe, when
FRMCTRL1.SET_RXENMASK_ON_TX
is enabled:
–
Sets RXENABLE[6]
–
The receiver is enabled after transmission completes.
•
Setting
RXENABLE
!= 0x00 by writing to RXENMASKOR:
–
Does not abort ongoing transmission/reception.
The receiver is turned off by the following actions:
•
The SRFOFF strobe:
–
Clears
RXENABLE[7:0]
–
Aborts ongoing transmission/reception by forcing the transition to IDLE mode.
•
Setting
RXENABLE
= 0x00 by writing to RXENMASKAND
–
Does not abort ongoing transmission/reception. Once the ongoing transmission/reception is
finished, the radio returns to the IDLE state.
There are several ways to manipulate the
RXENABLE
registers:
•
The SRXMASKBITSET and SRXMASKBITCLR strobes (affecting
RXENABLE[5]
)
•
The SRXON, SRFOFF and STXON strobes, including the
FRMCTRL1.SET_RXMASK_ON_TX
setting
23.9.2 RX State Timing
The receiver is ready 192
μ
s after RX has been enabled by one of the methods described in
. This is referred to as RX turnaround time in [1].
When returning to receive mode after frame reception, there is by default an interval of 192
μ
s where SFD
detection is disabled. This interval can be disabled by clearing
FSMCTRL.RX2RX_TIME_OFF
.
23.9.3 Received Frame Processing
The radio integrates critical portions of the RX requirements in IEEE 802.15.4-2003 and -2006 in
hardware. This reduces the CPU interruption rate, simplifies the software that handles frame reception,
and provides the results with minimum latency.
During reception of a single frame, the following frame-processing steps are performed:
(1)
Detection and removal of the received PHY synchronization header (preamble and SFD), and reception of
the number of bytes specified by the frame-length field.
(2)
Frame filtering as specified by [1], section 7.5.6.2, third filtering level.
(3)
Matching of the source address against a table containing up to 24 short addresses or 12 extended IEEE
addresses. The source address table is stored in the radio RAM.
(4)
Automatic FCS checking, and attaching this result and other status values (RSSI, correlation and source
match result) to received frames.
(5)
Automatic acknowledgment transmission with correct timing, and correct setting of the frame pending bit,
based on the results from source address matching and FCS checking.
Figure 23-10. Single Received Frame and Transmitted Acknowledgement Frame
234
CC253x Radio
SWRU191C
–
April 2009
–
Revised January 2012
Copyright
©
2009
–
2012, Texas Instruments Incorporated