51
Raveon Technologies Corp.
Result: Data will be received. 1236 ANDed with FFF0 is 1230. 1234 ANDed with FFF0 is
1230. The results of the ANDing match, and thus the data will be received.
Example 4 (able to receive from a group, xx34 where xx is any two digits)
Sending Destination Address =
2234
Receiving
M6
’s Unit Address =
1234
Receiving
M6
’s Address Mask =
00FF
Result: Data will be received. 2234 AND 00FF equals 0034. 1234 AND 00FF equals 0034,
therefore they match. The results of the ANDing match, and thus the data will be received.
Time Slots
The
M6G
uses a transmission scheme popular in mobile-telephones called
TDMA (Time Division Multiple Access). Each
M6G
is allocated a time-slot to
use for sending and receiving radio messages.
Refer to Section
Error! Reference source not found.
for detailed explanation of
the TDMA scheme. The important point to understand is that for optimum
efficiency in a
M6G
system, begin sequentially numbering the MYID of the
M6G
transponders at ID 0001. The second M6G should be ID 0002, and so on.
The
M6G
transponders have internal clocks with 20 ticks-per-second. They can
measure time and initiate transmissions 20 times every second (every 50mS).
The TDMA time slot is configured to be some number of these ticks. The factory
default allocation is 4-ticks for one time-slot. So each TDMA time slot is 200mS
long, and thus in 10 seconds, up to 50
M6G
transponders may report position.
These parameters are programmable, and may be re-configured based upon the
type of system they are used in.
8.8.
Local NMEA data from the internal GPS
The M6G GPS transponders and the Atlas PL personal locators may be
configured to output NMEA 0183 GPS messages from its internal GPS receiver.
For GPS tracking, these GPS transponders can receive GPS position reports
from other radios, and they may also be configured to output their own GPS
location via their serial port.
Following is a list of the NMEA messages that are available (as of revision C2 of
the Firmware).
NMEA
Message
Bit Number
(zero based)
Bit Mask
(hex format / decimal)
GGA
0
0×001 / 1
GLL
1
0×002 / 2
RMC
9
0×100 / 256
!AIVDM
10
0x200 / 512
