
			MEX Newsletter #001

Date: 	 05-09-84
From:    Ron Fowler
MEX rev: 1.00

This is the first in what will probably be a series of informative notes for
the MEX communications program.  These newsletters will provide bug fixes,
tips, applications information, etc. for users of MEX.

In order to avoid the daily-revision syndrome that was such a problem for
users of MDM7, important bug fixes will be provided in the newsletter whenever
possible, in a form useable in a READ file.  The hitherto undocumented
POKE command will be used to install patches; you can use the CLONE command
to save the patched program.

------------------------------------------------------------

These minor bugs have been found in the initial release of MEX: 

1) Certain commands result in screen output that contains a graphics or rev-
   erse video character; these commands are typically those which list key-
   words out of a table (the '?' command, "STAT ?", "HELP ?", etc).  These
   keywords have the high-bit set in the last character of the keyword, and
   MEX doesn't reset that bit.

2) For Alternate Long Distance Numbers: if an ALDN number is greater than
   12 characters, and the ALDN is specified on the command line, (eg,
   "[MEX] A0>>CALL <805-555-1212"), MEX misses any characters in the ALDN
   number beyond the 12th.

The following patch sequence will fix both problems.  Use your text editor to
copy the following 8 lines into a file (say, MEXFIX.MEX), then use the READ
command to execute it ("READ FIXMEX").  Make sure your MEX is still functional,
then use CLONE to save the fixed copy to disk (e.g., "CLONE NEWMEX.COM").


POKE $0E6A $CD $B3 $14 $D8
POKE $0E6E $3E $0C $EB $CD
POKE $0E72 $01 $46 $EB $C3 $DE
POKE $0E77 $12
POKE $0E78 $E6 $7F $21 $DC $52 $C3 $89
POKE $0E7F $43
POKE $12DA $C3 $6A $0E
POKE $4386 $C3 $78 $0E



This patch will be incorporated in the next revision of MEX (probly 1.01).

------------------

A number of users have reported that MEX disconnects them when any of the
exit-to-system commands (BYE, CPM, EXIT, SYSTEM) are entered.  The command

POKE $0168 $0C9

will fix that problem for most (again, CLONE your MEX to make the change
permanent).  This problem exists with several overlays, and relates to two
entries in the overlay jump table, usually called JMP$GOODBYE and JMP$DISCON
in MDM overlays (GOODBV and DISCV is MEX overlays).  MEX assumes that the
JMP$DISCON routine disconnects the phone; it is called on an X secondary
command or from the DSC command.  JMP$GOODBYE is called just prior to exiting
MEX and re-entering CP/M, providing a way for the overlay (if it needs to)
to "clean up" before CP/M gets control back.  Apparently MDM7 does not call
these routines in the same way, since several overlays have both of these
entries pointing to disconnect code.  Hence, an exit always disconnects.

I believe that these overlays are technically in error; JMP$GOODBYE should
have no reason to disconnect the phone.  Problem is, Irv Hoff never documented
the MDM overlay entry points (at least, as far as I know), so I can't be
sure of his intent.  In any case, I'd recommend that the offending overlays
be modified; this would make the change permanent (otherwise, the above POKE
must be executed each time a new MEX is generated).

------------------------------------------------------------

CIS protocol notes:

I didn't mention in the features list in -READ.ME (or in any of the announce-
ments that I sent out) that MEX is capable of file exchange with Compuserve,
using their "A" protocol.  Do "HELP CIS" for a little more information about
this feature.  If you don't use Compuserve and resent having valuable buffer
space taken up by Compuserve code, do "HELP COLD" for information on how to
remove the Compuserve code altogether, and reclaim the space for buffers.

Some notes on file-append:

Also not mentioned in the announcements was the "A" secondary option for the
T, E and L commands: this one lets you append to the end of an existing term
file (do "HELP APPEND" for more information on the "A" option).  I should
point out that some text editors write out files that are not compatible with
the way MEX does a file-append.  The algorthm used by MEX allows a fast
seek-to-end, and works like this:

	1) seek last physical record
	2) scan backwards until end-of-file mark found (1AH)
	3) scan backward until the first non-1A is found; this is
	   the last file character
	4) copy any previous characters in the record to the capture buffer

This should always work for files created by MEX; certain text editors, how-
ever, put a single 1A at the end of file, followed by random characters.  If
one of these random characters is a 1A, MEX will find a false end of file 
(after the real end), and newly-appended text will be "invisible".

Other editors do not put an end-of-file mark in the file if the text ends
on an even 128-byte boundary (ED.COM does this).  This too will cause problems
with the 'A' option.

Thus, unless you're sure your text editor legitimately writes the end-of-file
mark (and pads the last sector with EOF marks) it's best to use the 'A' option
only with files created by MEX.

READ files:

The documentaton doesn't mention it, but if you specify a READ file without
a filetype (eg, "READ CALLJOE"), MEX will assume a filetype of "MEX" (in fact,
a file named "CALLJOE" can't be found by MEX for this reason).

------------------------------------------------------------

It might not be clear from the documentation, but you can make your phone
numbers and keystring definitions a permanent part of MEX.  Simply define
the numbers you frequently use with the PHONE command (or LOAD a file from
disk), define your keystrings (or LOAD them), the do "CLONE <filename>".

You can, at any time, change the phone numbers or keystrings and re-CLONE;
MEX may be CLONEd any number of times.

------------------------------------------------------------

Misc. gotcha's:

0) In spite of what the documentation says, MEX will not run "out-of-the-box";
the overlay file must be installed first.  This was due to a change that was
made just prior to release.

1) It has been brought to my attention that, if you use the CLONE command with-
out a filename, MEX will write a filename of all blanks as the CLONE file.
Be sure to specify a name to the CLONE command; I'll make sure that the next MEX
does not allow all-blank filenames.

2) Another problem is that, if you specify a drive name with the filename for
the 'R' or 'S' commands (send/receive/Christensen protocol), MEX ignores
the command altogether. For now, just forego the drive name, and log into
the drive you want to send from or receive to.  This, too, will be repaired
in the next revision (this doesn't affect batch transmissions under the 'B'
secondary option).

3) Some users have had problems with keystring memory becoming corrupted; I'm
looking into the problem, but have not been able to corrupt my keystring
memory.  The most frequent complaint is that these garbage keystrings can't be
deleted with the KEY command. If you have this problem, do this:

	[MEX] A0>>COLD

This will erase your keystrings (*and* your phone numbers!), and allow you
to start over.  Nothing else will be disturbed.

4) The third line of the HELP file under LOAD (and SAVE) specifies an illegal
example for saving a phone number file:

	SAVE C:NEWPHONE.NUM

(phone number files must have a filetype of "PHN").



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