Microhard Systems MHX-2400, Operating Manual

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MHX-2400 Operating Manual: Chapter 3 Configuration Options
21
The Minimum and
Maximum Packet Size is
controlled by the Master.
The Slave and Repeater units
will use the Minimum and
Maximum Packet Size
setting from the Master.
S Register 111 - Packet Minimum Size
S Register 112 - Packet Maximum Size
S Register 116 - Packet Character Timeout
These settings determine the conditions under which the modem will
transmit accumulated data over the air.
S Register 111 - Minimum Size
Valid entries for this register are 1 to 255 bytes, which defines the minimum
number of bytes to receive from the DTE before encapsulating them in a
packet and transmitting over the air.
Note that the minimum packet size for all modems in the network is
determined by the Master only. This setting is ignored in all Slave and
Repeater modems. The default is 1 byte.
S Register 112 - Maximum Size
This setting has a range of 2 to 255, and defines the maximum number of
bytes from the DTE which should be encapsulated in a packet. This value
should be greater than the minimum packet size, but not smaller than is
necessary for reliable communications. If the wireless link is consistently
good and solid, a maximum size of 255 will yield the best throughput
(depending on the higher level protocols of the connected equipment).
However, if the link is poor (
e.g.
, experiencing excessive interference) and
data is frequently retransmitted, the maximum packet size should be
reduced. This decreases the probability of errors within packets, and
reduces the amount of traffic in the event that retransmissions are required.
Note that the maximum packet size for all modems in the network is
determined by the Master only. This setting is ignored in all Slave and
Repeater modems. The default is 255 bytes.
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-2400 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 9 ms. If set to 0 ms, the
unit will buffer exactly the minimum packet size before transmitting.