CC2430
Radio : Acknowledge Frames
these frames. This option is included for future
expansions of the IEEE 802.15.4 standard.
The MDMCTRL0.PAN_COORDINATOR control
bit must be correctly set, since parts of the
address recognition procedure requires
knowledge about whether the current device is
a PAN coordinator or not.
If a frame is rejected, CC2430 will only start
searching for a new frame after the rejected
frame has been completely received (as
defined by the length field) to avoid detecting
false SFDs within the frame.
14.19 Acknowledge Frames
incoming frames accepted by the address
recognition with the acknowledge request flag
set and a valid CRC. AUTOACKtherefore does
not make sense unless also ADDR_DECODE
and AUTOCRC are enabled. The sequence
number is copied from the incoming frame.
CC2430 includes hardware support for
transmitting acknowledge frames, as specified
in [1]. Figure 44 shows the format of the
acknowledge frame.
If MDMCTRL0L.AUTOACK is enabled, an
acknowledge frame is transmitted for all
Bytes:
4
1
1
2
1
2
Start of Frame
Delimiter
(SFD)
Frame
Control Field
(FCF)
Data
Sequence
Number
Frame Check
Sequence
(FCS)
Preamble
Sequence
Frame
Length
Synchronisation Header
PHY Header
(PHR)
MAC Header (MHR)
MAC Footer
(MFR)
(SHR)
Figure 44: Acknowledge frame format [1]
Two command strobes, SACK and SACKPEND
are defined to transmit acknowledge frames
with the frame pending field cleared or set,
respectively. The acknowledge frame is only
transmitted if the CRC is valid.
Using SACKPENDwill set the pending data flag
for automatically transmitted acknowledge
frames using AUTOACK. The pending flag will
then be set also for future acknowledge
frames, until a SACK command strobe is
issued. The pending data flag that is
transmitted will be logically OR’ed with the
value of FSMTC1.PENDING_OR. Thus the
pending flag can be set high using this register
control bit.
For systems using beacons, there is an
additional timing requirement that the
acknowledge frame transmission may be
started on the first backoff-slot boundary (20
symbol periods) at least 12 symbol periods
after the last symbol of the incoming frame.
When an acknowledge frame transmission
When
the
RF
register
control
bit
completes,
the
RF
Interrupt
flag
MDMCTRL1H.SLOTTED_ACK is set to 1, the
acknowledge frame is transmitted between 12
and 30 symbol periods after the incoming
frame. The timing is defined such that there is
an integer number of 20-symbol period
backoff-slots between the incoming packet
SFD and the transmitted acknowledge frame
SFD. This timing is also illustrated in Figure
45.
RFIF.IRQ_TXDONE will be set if this interrupt
source is selected by setting RF register bit
IRQSRC.TXACKto 1.
Acknowledge frames may be manually
transmitted using normal data transmission if
desired.
CC2430 Data Sheet (rev. 2.1) SWRS036F
Page 165 of 211
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