Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 156)

MFJ-1278B MULTI-MODE ADVANCED OPERATION
The actual value used will depend on the average number of queued up stations there are on
the channel during busy periods.
ACKWAIT (not directly user settable)
This timer actually consists of the sum of the 2 user settable parameters ACKTime and
DEAdtime. It represents the time the queued up TNC will wait before transmitting if it has
selected slot 0. This allows time for a completely inaudible (to this TNC) ACK to have been
sent on the channel without molestation. It was split into two timers because it has two
unrelated components. One is related only to the baud rate being used on the channel. The
other is related only to the absolute times the hardware requires to transport carrier
information from one station to another on the channel.
Other Related Parameters
Several of the existing TNC parameters will affect the operation of the modified protocol.
Most of these are parameters in TNCs on the channel which AREN'T using the new channel
access procedure. One, FRACK, must be set correctly in any TNC which IS using prioritized
ACK protocol.
FRACK should be set to a value which allows time for the TNC to send its packet AND
receive the ACK. This value will depend on the settings being used for PAClen and the radio
port baud rate. This is because, for some reason which I can't even begin to understand, the
FRACK timer starts at the BEGINNING of the packet rather than at the end. For this reason,
it is probably best to set FRACK to its worst case value for whatever baud rate you are using
on the radio port. This way you can make adjustments to PAClen without having to worry
about interaction with the setting of FRACK.
The FRACK settings that should be used (at least initially for BETA testing) are as follows:
BAUD RATE FRACK (SECONDS)
1200 3
300 8
Note that these settings apply when everyone on the channel is running the new protocol.
This assumes that all stations on the channel have both DWait and RESPtime set to 0.
If you are running the new protocol on a channel where some of the stations have long
RESPtime delays, those stations will not be able to successfully communicate with you after
connecting. If you wish to communicate with these stations you will have to set your FRACK
timer to a number which is longer than the other stations RESPtime delay.