Spread Spectrum Wireless Data Transceiver User Manual
M
ASTER
P
ACKET
R
EPEAT IN
M
ULTI
P
OINT
S
YSTEMS WITH
R
EPEATERS
The Master Packet Repeat parameter must also be set in MultiPoint Repeaters since they operate as a
Master to Slaves that connect to it. Therefore, the Repeater will send the packet out the number of times
corresponding to its Master Packet Repeat parameter. If this parameter is set improperly the reliability of
the overall system may be diminished. For example, assume the Master's Master Packet Repeat setting
is 3, and the link between the Master and Repeater is robust. Now assume that the Repeater's Master
Packet Repeat is set to 0, resulting in marginal communications between the Repeater and the Slaves it
is communicating with. The data communications between the Master and those Slaves communicating
through the Repeater will be marginal, because it is only as strong as the weakest link, which in this case
is the link between the Repeater and Slaves.
(2)
M
AX
S
LAVE
R
ETRY
The Max Slave Retry setting defines how many times (0 to 9) the Slave will attempt to retransmit a packet
to the Master before beginning to use a back-off algorithm.
3)
R
ETRY
O
DDS
While packets transmitted from the Master to the Slaves in a MultiPoint network are not acknowledged,
packets transmitted from Slaves to the Master are. It is possible, however, that more than one Slave will
attempt to transmit to the Master at the same time. Therefore, it is important that a protocol exists to
resolve contention for the Master between Slaves. This is addressed through parameters (2) Max Slave
Retry and (3) Retry Odds. Once the Slave has unsuccessfully attempted to transmit the packet the
number of times specified in Max Slave Retry it will attempt to transmit to the Master on a random basis.
The Retry Odds parameter determines the probability that the Slave will attempt to retransmit the packet
to the Master; a low setting will assign low odds to the Slave attempting to transmit. Conversely, a high
setting will assign high odds. An example of how this parameter might be used would be when
considering two different Slaves in a MultiPoint network, one with a strong RF link and the other with a
weak RF link to the Master. It may be desirable to assign a higher Retry Odd to the Slave with the weaker
link to give it a better chance of competing with the closer Slave for the Master's attention.
When Retry Odds = 0
the Slave will try to talk to the Master the number of times specified in the Max
Slave Retry parameter. If it is unsuccessful the Slave will purge its RS232 input buffer.
(4)
DTR
C
ONNECT
If set on the Slave at 0, the transceiver will transmit when RS232 data is received. A setting of 1
will cause it to connect to the Master when the DTR line goes high. With a setting of 2, the
transceiver will accumulate data in its buffer and transmit in a burst when the buffer is full. This
mode is valuable when a network has many low data rate devices and it is desirable to increase
overall network capacity. When set to ‘1’ if the ‘RTS to CTS’ function is enabled on the radio, then
‘RTS to CTS’ takes precedence over the ‘DTRConnect’.
Notes:
If ‘DTRConnect’ is set to ‘2’ and ‘RTS to CTS’ is enabled, then ‘RTS to CTS’ does not
work.
The transceiver has two separate transmit and receive user data buffers. For the FGR
series of radios these buffers are 2 kbytes in each. If one of the buffers overflow, the
transceiver will output unpredictable data.
(5)
R
EPEATER
F
REQUENCY
Repeater Frequency is set in conjunction with the Frequency Key in Menu (3) Edit Radio Transmission
Characteristics to use either the Master's hopping pattern (selection 0) or its own (selection 1).
The Repeater's hopping pattern must also be set in a MultiPoint network. This is accomplished with
parameter (5) Repeater Frequency. Setting this parameter is in contrast with Point-to-Point mode where
the Repeater automatically uses the Master's hopping pattern.
LUM0002AD Version
6.1
43
