AT commands
Networking and security commands
XBee/XBee-PRO S2C 802.15.4 RF Module User Guide
71
Default
Set in the factory
MM (MAC Mode)
The
MM
command is used to set and read the MAC Mode value. The
MM
command disables/enables
the use of a Digi header contained in the 802.15.4 RF packet. By default (
MM
= 0), Digi Mode is enabled
and the module adds an extra header to the data portion of the 802.15.4 packet. This enables the
following features:
n
ND
and
DN
command support
n
Duplicate packet detection when using ACKs
n
Remote command support
n
RR
command
n
DIO/AIO sampling support
n
OTA firmware updates
The
MM
command allows users to turn off the use of the extra header. Modes 1 and 2 are strict
802.15.4 modes. If the Digi header is disabled, the features above are also disabled.
When
MM
=
1
or
3
, MAC retries are not supported.
When the Digi header is disabled, encrypted data that is not valid will be sent out of the UART and not
filtered out.
Parameter range
0 - 3
Parameter Configuration
0
Digi Mode (802.15.4 + Digi header)
1
802.15.4 (no ACKs)
2
802.15.4 (with ACKs)
3
Digi Mode (no ACKs)
Default
0
RR (XBee Retries)
Set or reads the maximum number of retries the device executes in addition to the three retries
provided by the 802.15.4 MAC. For each device retry, the 802.15.4 MAC can execute up to three retries.
The following applies for broadcast messages: If
RR
=
0
, only one packet is broadcast. If
RR
is >
0
,
RR
+
2 packets are sent on each broadcast. No acknowledgments are returned on a broadcast.
This value does not need to be set on all devices for retries to work. If retries are enabled, the
transmitting device sets a bit in the Digi RF Packet header that requests the receiving device to send
an ACK. If the transmitting device does not receive an ACK within 200 ms, it re-sends the packet
within a random period up to 48 ms. Each device retry can potentially result in the MAC sending the
packet four times (one try plus three retries). Retries are not attempted for indirect messages that
are purged.
