User Manual

MHX-920 Operating Manual: Chapter 4 Configuration 23
PHP=1
PHP=2
PHP=1
SHP=2
Master
Repeater
Slave
Network 50
Hop Pattern 1
Hop Pattern 2
Figure 7 - Repeater
Operation
Master Repeater
Slave
Repeater
Slave
PHP=1
PHP=1
SHP=2
PHP=2
PHP=2
SHP=3
PHP=3
Hop-
Pattern 1
Hop Pattern 2
Hop Pattern 3
Figure 8 - A Network
Utilizing Three Hopping
Patterns
If there is no DTE connected
to the Repeater, turn off
handshaking (&K0) and set
the baud rate to 115K.
3)Slave. Up to 65535 Slaves may exist in a network, all of which
communicate with the common Master (either directly or via Repeater(s)).
Slaves cannot directly communicate with other. Slaves only provide
acknowledgement for packets of data sent by the Master when the Master is
in Point-to-Point mode. In multipoint mode, multiple slaves would conflict
with one another if they were all trying to acknowledge the Master at the
same time. The Master does, however, send acknowledgements to all
messages it receives from Slaves. The Master initiates communications by
sending a broadcast message to all Slaves. All Slaves are free to respond in
a “Slotted ALOHA” fashion, meaning that each Slave can choose one of
several windows in which to transmit. If there happens to be two Slaves
attempting to talk at the same time, the Master may not receive the data, and
the Slaves therefore would not get an acknowledgement. At this point, the
Slaves would attempt to get the information through at random time
intervals, thus attempting to avoid any more conflicts. Special parameters
which control the Slave’s response characteristics can be modified with S
Registers S115 and S213.
4) Repeater. A more precise title would be Repeater/Slave, because a
Repeater also has much of the same functionality as a Slave. A terminal can
be connected at the Repeater location and communicate with the Master
terminal. There is no restriction to the number of Repeaters in a network,
allowing for communication over virtually limitless distances. The presence
of one Repeater in a network automatically degrades system throughput by
half. Additional Repeaters, regardless of the quantity, do not diminish
system throughput any further. To understand Repeater operation, consider
the module as belonging to two hopping patterns at the same time: The
Primary Hopping Pattern and the Secondary Hopping Pattern. In Figure 7,
the Master belongs to Hopping Pattern 1, and communicates with the
Repeater on this hopping pattern. The Slave belongs to Hopping Pattern 2,
and communicates with the Repeater on this hopping pattern. The whole
system belongs to Network 50 (i.e., all units must be assigned the same
Network Address (S104), which in this case was selected to be 50. Note
that Slaves and Master only communicate on their respective Primary
Hopping Pattern. Repeaters communicate on the Primary Hopping Pattern
when communicating with the Master (or with another Repeater between
itself and the Master). Repeaters communicate on their Secondary Hopping
Pattern when communicating with Slaves (or with another Repeater between
itself and the Slaves). Figure 8 shows another example.
If the Repeater is not also being used as a Slave (there is no DTE connected
to the serial port), it is recommended that the Repeater’s baud rate be set to
115K, and that handshaking be disabled (&K0). This will help ensure a
smooth flow of data through the network.