Texas Instruments CC2541EMK User Manual

Length Byte
n
MPDU
MPDU
1
Correlation Value (Unsigned)
0
12
3
4
5
6
7
SRCRESINDEX
01234567
RSSI (Signed 2s Complement)
0
12
3
4
5
6
7
01234567
Data in RXFIFO
AUTOCRC = 0
MPDU
2
FCS
2
FCS
1
MPDU
n–2
••••
FRMCTRL0 Settings
AUTOCRC
APPEND_DATA_MODE
= 1 and
= 0
AUTOCRC
APPEND_DATA_MODE
= 1 and
= 1
CRC
OK
CRC
OK
RSSI (Signed 2s Complement)
M0114-01
2 1 2
MAC Header (MHR)
Bytes: 1 1
4
Preamble
Sequence
Start-of-Frame
Delimiter
(SFD)
Frame
Length
Frame
ControlField
(FCF)
Data
Sequence
Number
FrameCheck
Sequence
(FCS)
MACFooter
(MFR)
PHY Header
(PHR)
SynchronizationHeader
(SHR)
M0115-01
www.ti.com Receive Mode
23.9.7 Frame-Check Sequence
In receive mode, the FCS is verified by hardware if FRMCTRL0.AUTOCRC is enabled. The user is normally
only interested in the correctness of the FCS, not the FCS sequence itself. The FCS sequence itself is
therefore not written to the RXFIFO during receive. Instead, when FRMCTRL0.AUTOCRC is set, the two
FCS bytes are replaced by other more-useful values. The values that are substituted for the FCS
sequence are configurable in the FRMCTRL0 register.
Figure 23-15. Data in RXFIFO for Different Settings
Field Descriptions:
• The RSSI value is measured over the first eight symbols following the SFD.
• The CRC_OK bit indicates whether the FCS is correct (1) or incorrect (0). When incorrect, software is
responsible for discarding the frame.
• The correlation value is the average correlation value over the first eight symbols following the SFD.
• SRCRESINDEX is the same value that is written to RAM after completion of source address matching.
Calculation of the LQI value used by IEEE 802.15.4 is described in Section 23.10.4.
23.9.8 Acknowledgement Transmission
The radio includes hardware support for acknowledgment transmission after successful frame reception
(i.e., the FCS of the received frame must be correct). Figure 23-16 shows the format of the
acknowledgment frame.
Figure 23-16. Acknowledge Frame Format
There are three variable fields in the generated acknowledgment frame:
• The pending bit, which may be controlled with command strobes and the AUTOPEND feature (in the
FCF field)
• The data sequence number (DSN), which is taken automatically from the last received frame
• The FCS, which is given implicitly
241
SWRU191C–April 2009–Revised January 2012 CC253x Radio
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Texas Instruments CC2541EMK Specifications

General

Brand	Texas Instruments
Model	CC2541EMK
Category	Microcontrollers
Language	English