PacComm TINY-2 - Page 49

PACKET
RADIO
PROTOCOL
AX.25
Level
Two
of
the
values
in
the
right
column
of
the
table.
eC|R,
P|F
The
C(ommand),
R(esponse);
P(oll)
and
F(inal)
frame
types
are
only
used
in
AX.25
level
2
Version
2.0
mode.
These
types
are
not
displayed
for
packets
not
using
Version
2.0.
Sn
Sn
is
displayed
for
sequenced
information
D
frames.
’n’
is
the
frame’s
sequence
number
and
is
an
integer
0..7.
eRn
Rn
is
present
in
both
I
frames
and
RR-RNR-RE]J
frames.
The
’n’
value
monitored
shows
the
sequence
number
that
the
sending
station
expects
its
peer
will
use
for
the
next
new
sequenced
information
frame.
The
control
bytes
are
presented
in
hex
with
“x”
used
to
indicate
four
bits
which
depend
on
the
acknowledge
functions
the
packet
is
performing.
Usually
“x”
is
a
frame
number.
Frame
numbers
fit
into
three
bits
and
are
used
to
ensure
that
frames
are
received
in
order
and
that
no
frames
are
missed.
Since
only
three
bits
are
available,
the
frame
number
is
counted
modulo
8.
The
ame
parameter
has
a
ceiling
of
7:
no
more
than
seven
frames
can
be
“in
flight”
(transmitted
but
unacknowledged)
at
once.
AX.25
CONTROL
CODES
AND
MCOM
DISPLAY
CODES
Code
Abrv
Frame
Type
.
Code
Definition
xt
RR
Receive
Rdy
Cc
SABM
connect
x5
RNR
Receive
Not
Rdy
D
DISC
disconnect
x9
~=©REJ
Reject
UA
Unnumbered
ACK
o
8
86U!
Unnumbered
info
DM
Disconnected
mode
OF
DM
Disconnected
mode
FRMR_
Frame
reject
2F
SABM_
Connect
request
Ul
Unnumbered
info
43
~=DISC
Disconnect
request
Beacons,
ld,
etc.
63
UA
Unnumbered
Ack
RR
Explicit
ACK,
R
field
87
FRMR_
Frame
reject
RNR
-Revr
not
rdy,
R
field
even
|
Any
frame
endinginan
REJ
Reject,
R
fleid
even
number
(8A,
$C,
I
Sequenced
info
frms,
and
$E)
Is
an
info
frame.
both
S
and
R
fields.
42
el
This
and
UI
frames
are
the
only
frame
types
containing
user
data.
The
control
byte
contains
this
frame’s
number
and
the
number
of
the
next
frame
expected
to
be
received
from
the
other
end
of
the
link.
RR
Usually
used
to
acknowledge
receipt
of
an
I
frame.
The
RR
function
can
also
be
performed
by
sending
an
I
frame
with
an
updated
“expected
next
frame
number”
field.
eRNR
Used
when
the
buffer
space
on
the
receiving
side
is
full.
Operating
Manual,
4th Ed.
©
PacComm,
1990