FreeWave Technologies Inc. 218151431519 사용자 설명서
760 Mhz Data Transceiver Users Manual
LUM0000XX Rev A
Version 1.0
27
times. Therefore, it is important to find the optimal mix between network robustness, throughput, and
latency. In general, a setting of 2 to 3 will work well for most well designed networks.
latency. In general, a setting of 2 to 3 will work well for most well designed networks.
Note: The Master Packet Repeat may be set to 0 if the user software is capable of, or requires
acknowledgment. In this case if a packet sent by the Master and not received by the Slave, the
user software will control the retries as needed.
user software will control the retries as needed.
(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 (defined by the Retry Odds setting). Slave
retries will stop when an acknowledgement is received from the Master.
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)
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, 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.
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.
parameter and still not gained the Master’s attention, the Slave’s data buffer will be purged.
(4)
DTR
C
ONNECT
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.
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. These buffers are 2 Kbytes
each. In case of a buffer overflow, the transceiver will output unpredictable data.
each. In case of a buffer overflow, the transceiver will output unpredictable data.
(5)
R
EPEATER
F
REQUENCY
Repeaters are not available in the FreeWave 760 MHz Data Transceivers.
(6)
N
ETWORK
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 may be replaced
without reprogramming all of the Slaves in the network. Slaves will link with the first Master 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).
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 may be replaced
without reprogramming all of the Slaves in the network. Slaves will link with the first Master 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).