CC2420 Datasheet, PDF(42/92 Page) List of Unclassifed Manufacturers – 2.4 GHz IEEE 802.15.4 / ZigBee-ready RF Transceiver

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CC2420 Datasheet, PDF (42/92 Pages) List of Unclassifed Manufacturers – 2.4 GHz IEEE 802.15.4 / ZigBee-ready RF Transceiver

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AUTOACK may be used for non-beacon

systems as long as the frame pending

field (see Figure 19) is cleared. The

acknowledge frame is then transmitted 12

CC2420

symbol periods after the last symbol of the

incoming frame. This is as specified by [1]

for non-beacon networks.

Bytes: 4

Preamble

Sequence

Start of Frame

Delimiter

(SFD)

Frame

Length

Synchronisation Header

PHY Header

(SHR)

(PHR)

Frame

Data

Control Field Sequence

(FCF)

Number

MAC Header (MHR)

Frame Check

Sequence

(FCS)

MAC Footer

(MFR)

Figure 23. 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.

For systems using beacons, there is an

additional timing requirement that the

acknowledge frame transmission should

be started on the first backoff-slot

boundary (20 symbol periods) at least 12

symbol periods after the last symbol of the

incoming frame. This timing must be

controlled by the microcontroller by issuing

the SACK and SACKPEND command strobe

12 symbol periods before the following

backoff-slot boundary, as illustrated in

Figure 24.

If a SACK or SACKPEND command strobe

is issued while receiving an incoming

frame, the acknowledge frame is

transmitted 12 symbol periods after the

last symbol of the incoming frame. This

should be used to transmit acknowledge

frames in non-beacon networks. This

timing is also illustrated in Figure 24.

Using SACKPEND will 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.

Acknowledge frames may be manually

transmitted using normal data

transmission if desired.

Beacon

network

PPDU

Last PPSDAUCKsym/bSoAlBCaKcPkEofNfDslot boundary

12 Acknowledge

symbol

periods

12 symbol periods <=

tack

< 32 symbol periods

Non-beacon

network

PPDU

Acknowledge

tack = 12 symbol periods

Figure 24. Acknowledge frame timing

SWRS041B

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