MRF24XA_15 Datasheet, PDF (130/258 Pages) Microchip Technology – Low-Power, 2.4 GHz ISM-Band IEEE 802.15.4™ RF

MRF24XA
4.16 Base Time Units
Writing the BASETM<4:0> register bits selects the
desired Base time. Each increment of BASETM<4:0>
is equal to 1 µs.
The
RXACKWAIT<7:0>,
TXACKTO<7:0>,
BOUNIT<7:0>, STRMTO<15:0> and OFFTM<7:0>⁽³⁾
fields are specified in terms of Base time units.
The BASETM<4:0> bits must be unchanged while
RXEN = 1 or TXST = 1. The Base time is used in all
modes for all types of packets.
TABLE 4-5: BASE TIME UNITS
Function/Timer
Range of Timer with
BASETM<4:0> = 0x01
(1 µs resolution)
Range of Timer with
BASETM<4:0> = 0x02
(2 µs resolution)
Range of Timer with
BASETM<4:0> = 0x04
(4 µs resolution)
Time to Wait before
transmitting an ACK
packet
(RXACKWAIT<7:0>)
0-128 µs
0-256 µs
0-512 µs
Maximum time to look
for an ACK
packet before
issuing a TX ACK
Error or before
retransmitting
(TXACKTO<7:0>)
CSMA Backoff Time
(0 - (2^BE - 1) *
BOUNIT<7:0>)
0-256 µs
—
0-512 µs
0-1024 µs
BOUNIT<7:0> = 160^{(1, 2)}
(320 µs)
BOUNIT<7:0> = 80⁽²⁾
(320 µs)
BE = 0
—
0
BE = 1
—
0-320 µs
BE = 2
—
0-960 µs
BE = 3
—
0-2.24 ms
BE = 4
—
0-4.8 ms
BE = 5
—
0-9.92 ms
BE = 6
—
0-20.16 ms
BE = 7
—
0-40.64 ms
BE = 8
—
0-81.6 ms
RX Stream Timeout
(STRMTO<15:0>)
0-65 ms
0-131 ms
0-131 ms
Minimum OFF Time
(OFFTM<7:0> * 32)⁽³⁾
0-8 ms
0-16 ms
0-32 ms
Note 1: The maximum delay that MAC can support is 131 ms. Values outside this range may be set, but results in
truncation of the number to one that is less than or equal to 131 ms.
2: The value of 320 µs is chosen as it is the value referenced in the 802.15.4-2006 specification. Other val-
ues are possible, but may break 802.15.4 compliance.
3: Note that the OFFTM<7:0> register is the only timer value that is expressed not directly in BASETM units,
but rather is expressed in BASETM * 32 units.
DS70005023C-page 130
Preliminary
 2015 Microchip Technology Inc.