Microhard Systems MHX-2400, Operating Manual

Page: 19 / 46

MHX-2400 Operating Manual: Chapter 3 Configuration Options
15
PHP=1
PHP=2
PHP=1
SHP=2
Master
Repeater
Slave
Network 50
Hop Pattern 1
Hop Pattern 2
Figure 3 -
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 4 -
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 65534 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, nor can they
acknowledge packets of data sent by the Master. Clearly this would cause
conflicts when there are multiple Slaves. 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 3,
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 4 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.