
			    MEX Newsletter #004

Date:	  07-03-84       From:  Ron Fowler               MEX rev:  1.00

			    Batch bug Fix
		       MEX 1.10 pushed back
		    More on Fort Fone File Folder
		     Useable operating systems
			   M7 overlay notes
			     HELP bug
			    ALDS support
			      Support 

This is the fourth in a series of (hopefully) informative notes for users of
the MEX communications program.  These newsletters will provide bug fixes,
tips, and applications information.

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


Batch Bug Fix
-------------

The following bug is potentially quite serious; the patch should be in-
stalled as soon as possible if you use batch file transfers.

				-----

I've discovered a pointer calculation error in the batch file-lookup
routine.  This affects batch receive (only), and is only a problem if
the incoming batch file already exists on the disk.  In some circumstances,
the existing file will be left on the disk, and the succeeding file in
the directory will be erased and replaced with the incoming file.

To fix this, execute the following command, either from a READ file or
by typing it in at command level:

		POKE $429A $3C $00 $C8

(and then, of course, use the CLONE command to create a new MEX).

MEX 1.10 / 2.0:
---------------

At the moment, I'm involved in a full-scale TurboDOS implementation, which
is eating up most of my spare time.  Thus, I've had to push MEX 1.10 back
a month or two.  Hopefully I'll be able to get back to MEX development in
the next few weeks.

Contrary to rumor, MEX 1.10 will not be the commercial version hinted at
in the MEX documentation. The 1.10 release will fix all known bugs and add
a feature or two.

			   <soap-box dept>

Speaking of a "commercial" version, I've been accused of "using the entire
user community as a beta-test group in the eventual marketing of MEX".  Rather
than let this accusation go unchallenged, I'd like to mention the futility
of selling a program that I've already given away with no strings attached.
I will definitely not charge anybody anything for a bug-fix release.

It is likely, however, that MEX 2.0 will be a commercial effort; I think the
difference between MEX 2.0 and MEX 1.x will be as dramatic as that between
MEX and MODEM7 (it would have to be to find any significant customer base).
Among the things I'm considering for MEX2 are nested READS, full-blown
interpreted READ files (with incoming string-analysis conditionals and
success-codes returned by most commands), "background" printer support with
adjustable left, right, top and bottom margins, optional terminal support
(cursory x-y, insert/delete line, highlighting, etc), "server" mode, LBR
and SQ support, and an "overlay" structure (which would allow most of the
commands to be pulled out of the main program, shrinking it down to perhaps
10-14K).

Thus it would appear that MEX2 will require as much or more effort than
MEX1.  If this didn't justify at least a small return for my development
time, then I doubt if I would make the effort at all.


Fort Fone File Folder:
----------------------

Our local RCPM system is now up on brand new hardware, running a 40MB hard
disk (works out to about 36.5 MB after formatting).  Fort Fone is the best
(and perhaps the only) way to get timely answers to MEX questions.

The MEX documentation incorrectly listed the number of FFFF.  The number
is (414) 563-9932.


Useable operating systems:
--------------------------

I failed to mention in the original documentation that MEX does not run
under CP/M 1.4 (I was surprised to find that there is still a significant
CPM 1.4 user community!).  My apologies to anyone this inconvenienced.

In general MEX will run correctly under MP/M and TurboDOS, but requires
that the modem be interrupt-driven with minimum input queue size of 134
characters (single-tasking TurboDOS excluded).  I've written a TurboDOS
overlay that uses the built-in COMM channels for I/O, but it's a little
sluggish because of the overhead involved in the calling the O/S for modem
status ... I'll be adding some hooks in 1.10 to make this work better.

MEX should work correctly under CDOS (later releases) ... there is a flag
byte in MEXPAT (CDOSFL) that should be turned on under CDOS to prevent MEX
from making a disk-parameter request (which is not supported by CDOS).


M7 Overlay Notes
----------------

There are problems with a few MDM7 overlays when used with MEX.  Since I
seem to be answering these questions over and over, I'll go over them here,
and refer any future questions to this newsletter.

1) After installing my overlay, when I go into terminal mode, I get the
   message "modem overlay not installed".

   The problem is with the bit-status tests in the modem overlay.  I trapped
   all seven in the un-installed MEX, figuring all overlays would at least
   leave a "RET ! NOP ! NOP" in the associated jump table entries.  Not so.
   To fix this problem, simply modify your modem overlay to make sure that
   at least a "RET" is generated in any unused jumps.  These entries are
   located as follows:

	012AH   (in-modem-control-port)
	0134H   (out-modem-data-port)
	013EH   (in-modem-data-port)
	0148H   (mask-receive-ready)
	014BH   (test-receive-ready)
	014EH   (mask-send-ready)
	0151H   (test-send-ready)

2) Whenever I exit with the CP/M command, the modem disconnects.

   This one is a result of confusion between two overlay entry points.  The
   routine jumped to by the JMP$GOODBYE vector (0168H, called GOODBV in MEX
   overlays) should not disconnect the overlay -- this is the job of the
   JMP$DISCONNECT entry (0165H, called DISCV in MEX overlays).  GOODBYE is
   called expressly for overlays that need to "clean up" before returning
   to CP/M, and is called immediately before exiting to the operating sys-
   tem.  Some overlays use the same routine for both entry points, something
   that MDM7 allows for some reason.  To fix this, change the JMP$GOODBYE
   to point to a RET instruction.

3) My overlay works fine, but when I enter a baudrate into the phone num-
   ber library, it's ignored by MEX.

   Only MXO overlays are capable of changing baudrate from a phone library
   entry (and then, only if the overlay author writes the code).  This fea-
   ture uses a jump table entry present in MDM7 overlays, but implemented
   only for the PMMI modem, called PBAUD.  If you'd like to implement this
   feature, see the example code and notes in MXO-PMxx.ASM and MXO-GBxx.ASM,
   both of which have this feature included.


4) The overlay works fine, but using <esc>-P in terminal mode, to turn on
   the printer, doesn't have any effect.  The printer never outputs anything.

   The most common cause of this is a BIOS with list-status improperly NOT
   implemented (no typo there, read on...).  A CP/M BIOS that does not im-
   plement the list device status routine should always return A=0FFH (the
   ready condition); many, however, return A=0 (not ready).  Thus MEX never
   sees the printer as being ready, and never outputs characters.

   You can fix this by overlaying the LSTS vector in MEXPAT (located at 0D11H
   within MEX) with the address of a replacement routine in your overlay.
   For example, the following might be added to your overlay:

		PRTSTS: IN  PRPORT		;input status port
			ANI 80H			;test ready bit
			RZ			;return A=0 if not ready
			MVI A,0FFH		;else return A=255
			RET
	;
			ORG 0D11H		;patch the MEX vector
			DW  PRTSTS		


HELP bug
--------

A minor bug has been reported with open HELP files: if you do a READ (or
LOAD/SAVE) with an open HELP file, succeeding HELP commands get lost, and
print out garbage.  To recover from this, simply use the LOG command to
cause HELP to re-open its file with the next HELP command.


ALDS Support
------------

Apparently, I neglected to mention in any of the documentation files that
MEX supports Alternate Long Distance Service, up to a maximum of two such
numbers (although, for some reason, it doesn't seem to work with the An-
chor modem).  So I'll do it here.

To enter an ALDS number into your phone library, enter it as you would any
other number, except that its name must be '<' (left arrow) or '>' (right
arrow).  These two specially-named numbers may then be called out as a
prefix to any other number (whether in the phone library or entered on the
command line).

For example, let's say you access Sprint through the number 555-1234 and you
also have MCI service available through 555-4321. Enter the numbers in
the library this way:

		PHONE >=555-1234,,,,,99999   <=== include delays + user code
		PHONE <=555-4321,,,,,88888

Now, to route any call thru Sprint, simply prefix with a '>'.  For example,

		CALL >808-555-99999
		CALL >TECHCBBS
		CALL <CONOGA		<<--- this one uses MCI
	
You can also enter numbers in the library with a "built-in" sprint code:

		PHONE TECHCBBS=<909-555-3333

Support
-------

Finally, a short note about support for various overlays, machines, and so
on.  I've gotten several requests from people to write overlays for specific
machines, and some phone calls from people asking for help with debugging
their overlays.  The latter I don't mind doing, as time permits (but *please*
use the RCPM system instead of my voice line!); I don't have the time or
inclination, however, to write custom overlays.



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