User's Manual

MDS 05-2708A01, Rev. A MDS TransNET I/O Guide 29
The default selection is DCE. In this mode, CTS will go high following RTS,
subject to the CTS programmable delay time. Keying is stimulated by the input
of characters at the data port. Hardware flow control is implemented by
dropping the CTS line if data arrives faster than it can be transmitted.
If CTS KEY is selected, the radio is assumed to be controlling another radio,
such as in a repeater system. The RTS line is ignored and the CTS line is used
as a keyline control for the other radio. CTS is asserted immediately after the
receipt of RF data, but data will not be sent out the DATA INTERFACE port until
after the CTS programmable delay time has expired. (This gives the other radio
time to key.)
Following transmission of the last byte of data, CTS will remain asserted for
the duration specified by the
CTSHOLD command. CTSHOLD should be set
sufficiently high.
DMGAP [xx]
The DMGAP command sets the amount of time in milliseconds to wait after the
receipt of a character before interpreting the next received character as the start
of a new message. When data port baud rates are slow, the gap between
characters within a poll may be so long that the radio interprets the next
character as the start of a new poll. When diagnostics is being performed using
passive messaging, this command may be used to change this behavior.
HOPTIME
The HOPTIME command sets or displays the hop time setting. The command is
one of eight keywords whose parameters and related efficiencies are shown in
Table 6.
Although the default setting is 7, transmission efficiency can usually be
improved by using a setting of 28 when data rate exceeds 115200 bps. This is
because there will be less frequent channel hops when using this setting,
contributing to a smoother flow of transmitted data.
Other hop times can be used to customize performance based on SEND count
settings and payload data poll length.
The only time shorter settings (
SHORT through XSHORT) should be considered
is when the message size is very small and strong interference of a persistent
nature is occurring on many frequencies. In these cases, a shorter hop time may
improve the chances of a message getting through—but at the cost of reduced
channel efficiency.
Table 6. Hoptime parameters
Hop Time
Keyword
Time
per
Hop
Max.
Bytes
per Hop
Channel
Efficiency
XSHORT 10 ms 9 32.1%
16 16 ms 21 46.7%
20 20 ms 30 53.6%
25 25 ms 39 55.7%
32 32 ms 57 63.3%
SHORT 40 ms 72 64.3%
NORMAL 80 ms 162 72.0%
LONG 160 ms 336 74.5%