MRF24J40-ISLASHT datasheet(99/156 Pages) MICROCHIP

99 / 156 page

Preliminary

DS39776C-page 99

MRF24J40

3.8.1.2

BO and SO

Values of Beacon Order (BO) and Superframe Order

(SO) determine the Beacon Interval (BI) and

Superframe Duration (SD).

Beacon Interval (BI) in terms of BO can be expressed as:

BI = aBaseSuperframeduration * 2BO

Similarly, Superframe Duration (SD) in terms of SO can

be expressed as:

SD = aBaseSuperframeduration * 2SO

where aBaseSuperframeduration = 960 symbols.

BO and SO can be configured by programming the BO

(0x10<7:4>) bits and SO (0x10<3:0>) bits in the ORDER

and SO should be in the range, 0

≤ SO ≤ BO ≤ 14. If the

values of BO and SO are equal, then the superframe

does not have any inactive portion. A Beacon Interval

can be as short as 15 ms or a long as 251 seconds based

on the values of BO and SO.

3.8.1.3

GTS

If a device wants to transmit or receive during CFP, it

sends out a “GTS request” in the CAP to the PAN coor-

dinator. The PAN coordinator broadcasts the address

of the device number for that device in the beacon

frame if resources are available.

support

GTS

operation,

MRF24J40

uses

TXGTS1FIFO and TXGTS2FIFO. The TXGTS1FIFO

and TXGTS2FIFO are ping-pong FIFOs and can be

assigned to different GTS slots or to the same slots. If

both are assigned to the same slot, they take turns for

transmission within that slot. TXGTS1FIFO and

TXGTS2FIFO can be triggered ahead of their slot time,

but transmission from the FIFO will take place exactly

at the assigned slot time.

Refer to Section 3.12 “Transmission” for information

on how to transmit a data frame using the

TXGTSxFIFOs.

FIGURE 3-5:

GTSFIFO STATE DIAGRAM

GTSSWITCH = 1

Switch TXGTSxFIFO

if Transmit Error

TXGTS1FIFO

TXGTS2FIFO

Wait for GTS Slot

Transmit Complete

Transmit Error

(clear TXG1TRIG)

Transmit Complete

Transmit Error

(clear TXG2TRIG)

TXGTS1FIFO

TXGTS2FIFO

Wait for GTS Slot

Transmit

Complete

Transmit

Complete

Hold and Wait

until Next GTS

Transmit Error

(clear TXG1TRIG

and TXG2TRIG)

Transmit Error

(clear TXG1TRIG

and TXG2TRIG)

GTSSWITCH = 0

Hold and wait TXGTSxFIFO

if Transmit Error

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