![Texas Instruments CC2533 Скачать руководство пользователя страница 240](http://html.mh-extra.com/html/texas-instruments/cc2533/cc2533_user-manual_1094592240.webp)
SFD
LEN
- - - - -
When There Is No Source Address:
FCF + SEQ + Destination
SFD
Interrupt
RX_FRM_ACCEPTED
Interrupt
RX_FRM_DONE
Interrupt
Last
Byte
SRC_MATCH_DONE
Interrupt
SFD
LEN
- - - - -
When There Is a Source Address:
FCF + SEQ + Desti
Source PAN ID
SFD
Interrupt
RX_FRM_ACCEPTED
Interrupt
RX_FRM_DONE
Interrupt
M0113-01
Last
Byte
Source
Address
SRC_MATCH_FOUND interrupt
may occur during this interval
SRC_MATCH_DONE interrupt
occurs during this interval
Receive Mode
When source address matching is enabled and the matching algorithm completes, the
SRC_MATCH_DONE interrupt flag is set, regardless of the result. If a match is found, the
SRC_MATCH_FOUND flag is also set immediately before SRC_MATCH_DONE.
illustrates the timing of the setting of flags:
Figure 23-14. Interrupts Generated by Source Address Matching
Tips and Tricks
•
The source address table can be modified safely during frame reception. If one address replaces
another while the receiver is active, the corresponding enable bit should be turned off during the
modification. This prevents the RF Core from using a combination of old and new values, because it
only considers entries that are enabled throughout the whole source matching process.
The following measures can be taken to avoid the next received frame overwriting the results from source
address matching:
•
Use the appended SRCRESINDEX result instead of the value written to RAM (this is the
recommended approach).
•
Read the results from RAM before RX_FRM_ACCEPTED occurs in the next received frame. For the
shortest frame type, this happens after the sequence number, so the total available time (absolute
worst-case with a small safety margin) becomes:
16
μ
s (required preamble) + 32
μ
s (SFD) + 128
μ
s (4 bytes) = 176
μ
s
•
To increase the available time, clear the
FSMCTRL.RX2RX_TIME_OFF
bit. This adds another 192
μ
s,
for a total of 368
μ
s. This also reduces the risk of RX overflow.
240
CC253x Radio
SWRU191C
–
April 2009
–
Revised January 2012
Copyright
©
2009
–
2012, Texas Instruments Incorporated