AEA PAKRATT PK-232, Technical Reference Manual

Page: 26 / 101

PK-232 TECHNICAL MANUAL CHAPTER 4 – HOST MODE AND SPECIAL APPLICATIONS
PK232TM Rev. A 5/87 4-9 Page 26
In communications mode other than Packet, received data is formed into blocks one char-
acter at a time, for total of four bytes per block (SOH, CTL, data, ETB).
4.4.3 Special Case in AMTOR
AMTOR operation produces some special responses.
o When the PK-232 is in Mode A (ARQ), data received from another station is block
type $30.
o When the PK-232 is in Mode B (FEC), S (SELFEC) or L (ALIST) block type $3F is
used.
4.4.4 Link Messages
Link messages have the following format:
SOH $5x (message) ETB
Some of these link messages are:
CONNECTED to <callsign>
<callsign> busy
Connect request: <callsign>
FRMR sent: xx yy zz
FRMR rcvd: xx yy zz
Retry count exceeded
DISCONNECTED: <callsign>
LINK OUT OF ORDER, possible data loss
(3 bell characters, output from CBELL)
Transmit data remaining
4.5 Host Mode and Special Packet Applications
Certain differences exist when operating in Packet mode using the Host mode.
o Data is packetized only after the ETB character.
o PACTIME and CPACTIME are ignored.
The Host mode permits the use of special machine-oriented interfaces that are inappropriate
for direct interpretation by human users.
4.6 Raw HDLC
Raw HDLC is available only in Host mode. When RAWHDLC is set to ON, data sent from the
computer to the PK-232 is converted to pure Packet frames without adding headers or pro-
tocol bytes.
In RAW HDLC, the host computer must provide the AX.25 header with each outgoing frame.
Raw HDLC moves the AX.25 protocol from the PK-232 to the host computer, permitting the
system operator to create his own version of AX.25, with possible inclusion of layer 3 and
higher-level protocols, as well as protocols other than AX.25.
Data from the PK-232 to the computer included every byte in the received frame, minus
flags and checksum.