Timewave PK-900, Operating Manual

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A B C D E F G 0 x H I J K L M 0 N O P Q R S T 0 y U V W X Y Z 1
The least significant bit of each byte is used to show whether or not
the byte is the final byte in the address field, as in standard AX.25.
The bits "x" and "y" (lower case) have the function of command and
response, similar to the function of the standard AX.25 version 2.0
SSID byte C bits (see AX.25 Protocol version 2.0, section 2.4.1.2).
In the AEA implementation of Lite addressing, the standard callsigns
are compressed to yield short addresses. The destination callsign is
compressed into bits A-M, and the source into N-Z. These bits are
used as the address field suggestion following the control byte in the
Connect (SABM) frame. When the bits are used following the control
byte as an ID suggestion or a real extended ID, the format is:
0 A B C D E F G 0 0 H I J K L M 0 N O P Q R S T 0 0 U V W X Y Z
If we label the 7 standard right-justified callsign bytes 1-6 and
SSID, here is how we derive the first group of address bits A-M:
ABCDE = (byte 1 XOR byte 4) AND $1F
FGHI = (byte 2 XOR byte 5) AND $0F
JKLM = (byte 3 XOR byte 6 XOR SSID) AND $0F
AEA firmware derives the second group of bits N-Z the same way. Other
implementations are free to select any combination of 26 bits when
setting up the short address in either the initial SABM frame or its
UA response.
4.12 Packet Meteor Scatter Extension
A new packet protocol extension has been added for meteor scatter
work that allows a Master/Slave packet connection to be established.
This is done to reduce the possibility of simultaneous transmissions
by both sides of a packet connection over a long meteor scatter path.
This experimental protocol is activated by turning User BIT 18 ON
(UBIT 18 ON). When UBIT 18 is ON (default OFF) the packet station
who initiates a packet connect will become the Master station and the
station who acknowledges the connect becomes the Slave.
After a Meteor Scatter connection has been established, the Master
station will continually send either information frames (I-frames)
or polling frames and await an acknowledgement from the slave. The
Master station therefore sends packets constantly, even if all its
I-frames have been acknowledged. The slave station sends nothing,
not even I-frames, until it receives a polling frame from the master.
The Slave station may only send an I-frame to the Master after a
poll frame has been received.
The packet timing of the Master station is critical for proper Meteor
Scatter operation. In a normal AX.25 packet connect, the FRACK timer
counts down until it reaches zero and then a Retry of a poll frame is
sent. The FRACK timer counts in units of seconds however and a finer
timing resolution is desirable for Meteor Scatter work. A new timer
called FRICK has been added which times in 10 mSec increments. The
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