FreeWave Technologies Inc. 121819DEE521 Manual De Usuario
LRS-455-EU Data Transceiver Users Manual
LUM0032AA Rev A
Version 1.0
18
(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.
(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.
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
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.
Note:
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.
(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).
Without having the serial numbers in the Call Book, a Slave may establish communications with different
Masters, though not at the same time. This is very useful in mobile MultiPoint applications.
(8)
M
ULTI
M
ASTER
S
YNC
MultiMaster Sync is reserved for applications, in both Point-to-Point and MultiPoint modes, with
concentrations of Master units where it is necessary to reduce interference between the Masters. Please
contact FreeWave Technologies for more information.
(9)
1
PPS
E
NABLE
/D
ELAY
The 1 PPS Enable/Delay option allows the radio network to propagate a 1PPS signal from the Master to
all Slaves in a MultiPoint network. When this parameter is enabled a properly generated pulse applied on
the DTR line of the Master will provide a 1 PPS pulse on the CD line of any Slave in the network. To use
the 1 PPS Enable/Delay feature the steps outlined below must be followed: