AEA PAKRATT PK-232, Technical Reference Manual

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PK-232 TECHNICAL MANUAL CHAPTER 4 – HOST MODE AND SPECIAL APPLICATIONS
PK232TM Rev. A 5/87 4-1 Page 18
CHAPTER 4 – HOST MODE AND SPECIAL APPLICATIONS
4.1 Introduction to Host Mode
In conventional AX.25 Packet operation, the PK-232 presents a reasonably 'user-friendly' ver-
bose human interface that uses plain-language command words up to eight-letters that ac-
tually spell out a word.
The CONNECT command, for example, describes exactly what the command does; the PK-
232 transmits a Connect Request (SABM) frame. In addition, when you want to know the
connect path and other connection characteristics, you type
CONNECT and the PK-232
sends your computer the following:
Link state is: CONNECTED to N6IA via W6AMT; v2; 1 unACKed
all of which tells you that:
o you are connected to N6IA through the W6AMT digipeater;
o you have AX25L2V2 set to ON;
o you have sent a frame to N6IA which he has not acknowledged yet.
4.1.1 Why Do We Need a Host Mode ?
You may wish to write a program that permits your computer to control your PK-232. You
could write a program that provides a split screen with status windows. You might want to
include a personal mailbox, a multi-user bulletin board system, an automatic calling rou-
tine, with tutorials or help screens. you may also wish to experiment with some high-level
protocols or techniques other than AX.25 Level 2. Your program could be written to take
much of the burden of operating a data controller and free you from the need to memo-
rize the PK-232 commands and possibly permit fully-automatic system operation.
When working with conventional, human-oriented data controllers and Packet TNCs, your
hypothetical program must interpret and translate all the verbose, human-interface infor-
mation sent in either direction over the serial interface between your computer and your
PK-232. All PK-232's command and response features that permit convenient human oper-
ating unfortunately produce substantive difficulties for a computer. For example, your
computer and program must:
o decide if the PK-232 is in command mode or converse mode;
o sort through status messages in English;
o accept any data or status from the PK-232 at any time.
4.1.2 How Does Host Mode Help Us ?
Host mode does not use human-type dialog. By communication directly with the "host" or
computer, Host mode provides the computer with much greater direct control over the PK-
232. Host mode permits programmers to eliminate, reduce or greatly simplify the transfer
and subsequent encoding and decoding of critical information, eliminating wasteful and
redundant information. In Host mode, the PK-232 is 'unfriendly'; humans would find it dif-
ficult to operate the PK-232 in Host mode.
Host mode uses the normal RS-232 serial link between the PK-232 and the computer, but
provides a more efficient link with fewer characters necessary.