User's Manual

Spread Spectrum Wireless Data Transceiver User Manual
LUM0002AF Rev D Version 6.3 44
Slaves communicating through this Repeater will only receive the initial packet from the Master with no
repeats. Therefore, if the packet is not received on the first try, the Slave will not respond as expected.
(2)
MAX SLAVE RETRY
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 (defined by the Retry Odds setting). Slave
retries will stop when an acknowledgement is received from the Master.
(3)
RETRY ODDS
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, 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 higher 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 higher Retry Odds to the Slave with the weaker link to give it a
better chance of competing with the closer Slave(s) for the Master's attention.
When Retry Odds = 0, after the Slave has exhausted the number of retries set in the Max Slave Retry
parameter and still not gained the Master’s attention, the Slave’s data buffer will be purged.
(4)
DTR CONNECT
With the setting of 0 in the Slave, the transceiver will transmit when RS232 data is received. A setting of
1 will form a Point-to-Point link with the Master when the DTR line is high. With a setting of 2, the
transceiver will transmit in bursts. This mode is valuable when a network has many low data rate devices
and it is desirable to increase overall network capacity.
Note: If ‘DTRConnect’ is set to 1 and the ‘RTS to CTS’ function is enabled on the radio, then ‘RTS to
CTS’ takes precedence over ‘DTRConnect’.
Note: If ‘DTRConnect’ is set to ‘2’ and ‘RTS to CTS’ is enabled, then ‘RTS to CTS’ is ignored. The
transceiver has two separate transmit and receive user data buffers. For the FGR series radios,
these buffers are 2 Kbytes each. In case of a buffer overflow, the transceiver will output
unpredictable data.
(5)
REPEATER FREQUENCY
Repeater Frequency must be set to a 1 in a Repeater when a FreqKey other than that of the Master is
desired. This condition occurs when parallel Repeaters in a network may have overlapping areas of
responsibility. The default setting of 0 causes the Repeater to use the FreqKey set in Menu 3.
Note: When Repeater Frequency is set to 0 the FreqKey setting must match the Master or Repeater
acting as the Master for the transceiver.
(6)
NETWORK ID
NetWork ID allows MultiPoint networks to be established without using the Call Book. The default setting
of 255 enables the Call Book. To enable NetWork ID the value must be set between 0 and 4095
(excluding 255). Since NetWork ID does not use serial numbers, MultiPoint Masters and Repeaters may
be replaced without reprogramming all of the Slaves in the network. Slaves will link with the first Master
or Repeater that it hears that has a matching NetWork ID. The Network ID function should be used in
conjunction with the SubNet ID feature (If necessary).