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TNC2KISS.DOC
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1987-05-26
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Date: Wed 1 Oct 86 18:56:07-EDT
From: Mike Chepponis <cadre!C.CS.CMU.EDU!Michael.Chepponis@pitt.UUCP>
OK, Alpha testers, go to it! A few notes: I believe that we should keep the
download ROM in the TNC-2, so that as we make improvements to the KISS TNC
code (and as we figure our what we REALLY need) we will not have to re-blow a
ROM; Phil's stuff can automatically download this file upon startup.
Implementation: The 3 frames to the TNC to set TXdelay, Persistence and
Slot Time are implemented, as well as a type "4", for setting the TX Tail
timer (the last flag has to leave the SIO, so this number should be at least
2). The defaults are TXdelay 300ms, Persistence 128, Slot Time 50ms and
TX Tail timer 20ms.
All frames coming to the TNC need not be preceded by a FEND char, but all
frames coming from the TNC will have an FEND at the beginning and at the end
of the frame.
The STA LED blinks at a 1 Hz rate. If this LED stops blinking, the TNC has
crashed. The CON LED lights up when the TNC is sending frames to the host.
The TNC can be run "unsquelched" if you don't want to pay the squelch opening
time; just turn the receiver squelch off.
The buffers are fixed length, 124 chars per buffer. There are about 100
buffers free in a 16k RAM system, and about 230 buffers in a 32K RAM system.
If you run out of buffer space (by sending too much stuff to the TNC), it will
halt. I wasn't sure what the right thing to do was, so the TNC just halts in
this case. So don't send too many outstanding buffers to the TNC.
No flow control is used.
The size of the transmitted and received frames is limited only by buffering
space. In particular, you can send very large frames to cut down on header
overhead & beat the VC gang on that count! The Zilog Ap note suggests
limiting frames to 4096 or fewer characters, however, because they claim that
the CRC doesn't work as well for very large packet sizes. So be reasonable!
Any particular packet can be as large as available buffer space. In my case
(with a 32k RAM) I can send about a 28k packet. You should always install
JMP 4 on the TNC to disable the (hardware) TX timeout timer.
I guess that's it. Let me know the bugs you find. Good Luck, -Mike
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Changes since V1:
Light no longer blinks to let you know TNC is alive, instead, STA and CON
used to show traffic to and from PC, while CAR and PTT are used for what
you would expect, radio side send and receive indicators.
Bug fixes, does not seem to crash anymore.
-------
Changes since V2:
Hey guys, I have v0.3 of kiss ready - at least, it seems OK here. I am going
to send you guys 3 more messages: 1) kiss source 2) kiss download hex and
3) kiss .hex ORGed at 0
I have no way (at the moment - we're working on it) to test (3). It is meant
to be burned into a ROM and run from that ROM. As to hooking up to howie's
code, I left some EQUates in the source and you can see what I had in mind. It
will need some hacking to work with howie's code. When I get my prom burner,
I will mess with it if you guys don't want to. I still want to include the
hex loader in this code, which would get activated on power-up with a ":"
command (and howie code with an H or h and kiss itself with ^E - but this is
all just conjecture at the moment.)
The biggest difference in kiss, besides now supporting full duplex (code 05 01
makes it full duplex, code 05 00 puts it back to the (default) half duplex), is
that there is a positive indication that the code has been dowloaded / is
running correctly. Immediately after successful download (or power up if in
ROM) the STA and CON LEDs will flash on & off 6 times, at about 1 Hz. If you
have 8k RAM, only the CON LED will flash. If you have 16k RAM, only the STA
LED will flash. If you have 32k, both LEDs will flash.
As I said, I haven't noticed any problems with this code, but you should (and
I'm sure, will) point out deficiencies. Oh, I changed a bunch of default
values, too. The txdelay is a bit longer, the persistence is 64 and the tail
timer is 3 instead of 2. These are probably not big things, and anyway, you
can customize your setup in /autoexec.net anyway.
I am especially interested in how (if?) the orged at 0 "rom" version works.
CUL & gl -Mike
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