User Manual

30 MHX-920 Operating Manual: Chapter 4 Configuration
S Register 114 - Packet Size Control
This register, when set to 1, allows for Repeater and Slaves’ local S111 and
S112 to override those of the Master when the system is operating in point-
to-point mode. This may be useful for controlled asymmetrical data flow.
The master always transmits in the first portion of the hop interval, with
slaves and repeaters responding back to the master on the second portion of
the hop interval. Setting the master’s max packet size smaller than that of
the slave would ensure that the master uses less of the available time within
the hop interval for transmitting data, thereby allocating more time for the
slave.
S Register 116 - Packet Character Timeout
This register has valid entries of 0 to 254 milliseconds. The Packet
Character Timeout timer looks for gaps in the data being received from the
DTE. The timer is only activated after the Minimum Packet Size has been
accumulated in the modem. After which, if the timer detects a gap in the
data exceeding the Packet Character Timeout value, the modem will
transmit the data.
The MHX-920 will accumulate data in its buffers from the DTE until one of
the following requirements is met (whichever occurs first):
• The Maximum Packet Size (in bytes) has been accumulated;
• The Minimum Packet Size has been accumulated AND the Packet
Character Timeout interval has elapsed.
The default for the Packet Character Timeout is 8 ms. If set to 0 ms, the
unit will buffer exactly the minimum packet size before transmitting.
S Register 113 - Packet Retransmissions
This register applies to both Master and Repeater operation. It does not
apply to Slave operation. In point-to-multipoint mode, the Master will
retransmit each data packet exactly the number of times defined by the
Packet Retransmissions parameter. In point-to-point mode, the Master will
only retransmit the packet if it does not get an acknowledgement from the
slave with which it is communicating. In this case, the Master will continue
to retransmit until an acknowledgement is received, or the retransmission
limit is reached. When the retransmission limit is reached, the Master
discards the packet. The Master retransmits once at the beginning of each
hopping interval until the limit is reached. This parameter is not necessary
in Slave units since all Slaves receive acknowledgement from the Master,
and needn’t blindly retransmit if it has knowledge that the Master has
received the packet.. As discussed previously, the Repeater effectively
behaves as both a Master and a Slave. When the Repeater is tuned to its
Secondary Hopping Pattern (acting as a Master), the Packet Retransmissions
Parameter comes into play. The Repeater will re-send packets of data on to
Slaves or other Repeaters exactly the number of times defined by the Packet
Retransmissions parameter.
Recipients of the packet will discard any duplicates The valid settings for
this parameter are 0 to 255 retransmissions. The default is 1.