The World of Computer Software/The World of Computer Software.iso/suprabbs.zip/V32_Q&A.TXT

Text File | 1992-05-12 | 12KB | 198 lines

             SUPRA TECH BULLETIN
          Important SupraFAXModem V.32bis Information
                  5/11/92


Congratulations on your purchase of a new SupraFAXModem V.32/V.32bis.
You've just bought the latest in state-of-the-art modem technology.  This
product is designed to be plug 'n play for most users.  However, some software
and computers may have problems properly communicating at high speeds with
your new modem because they were designed without anticipating this new level
of performance.  This bulletin is designed to help you avoid problems and
provide more up-to-date information.  Please read it carefully, as it may
save you substantial time tracking down any problems.  We will be updating
this bulletin as we collect more current information.  The most current data
we have is always available on the Supra BBS at [phone].  We recommend
you use the BBS as your first source for up-to-the-minute information.

Modem Compatibility
We have tested the SupraFAXModem V.32bis with nearly all major brands of
modems with excellent results.  At this time, we have not identified any
major brand that does not work properly with the protocols we support.
If you cannot make a connection, it is possible that the modem uses a
proprietary protocol that we do not support.  Some of these include US
Robotics HST, CompuCom, Telebit, and Hayes V Series.  You should be able to
communicate with most of these at 2400 bps.  Some of these modems feature
"dual-standard" operation, with their proprietary standard as well as V.32 or
V.32bis.   However, if the dual-standard feature has not been configured
properly, you may not be able to connect at V.32 or V.32bis.  It is also
possible that the remote modem may need a firmware upgrade if it was
purchased more than a year or two ago.  Several pioneers in the high-speed
modem business have released multiple upgrades to fix compatibility problems
with early units.

Line Noise Problems
As a general rule, the faster that you are communicating, the better your
phone lines need to be.  When you get up to 9600 and 14,400 bps, it is
critical that you have clear lines from end to end.  Noise can be introduced
by your local premise wiring, the local or long distance connection, or at
the remote premise.  Some problems you may be able to fix, and some you can
not.  If you have problems with every high-speed attempt, you should try
using the modem at another location to determine if that corrects the
problem.  If so, check your local wiring or phone system.  If the problem
occurs occasionally when calling the same location it is probably a long
distance connection problem.  You may want to try a different company or dial
the 10288 prefix to get an AT&T line.  If you only have problems when calling
one location, it is probably a problem on their end.  The V.32bis
specifications state that modems must be able to shift down or up in speeds
when the remote modem requests it to do so usually in response to line noise
problems.  However, initiating this request to change speeds is optional to
implement and is not provided on many modems, including the SupraFAXModem
V.32bis.  We will change speeds, we just won't initiate the process.  For
some people this may be important and we anticipate supporting it in a later
version of firmware that will be available at low or no cost.  Be sure to
send in your warranty card so we have you in our records.  If you anticipate
having problems, you can lock the modem to lower connection speeds by
changing its software configuration.  First, issue the AT N to enable
specifying the connection rate,  Next, you can issue AT S37=0 to connect at
your serial port rate (set rate to 9600 bps for example) or you can set S37
to the maximum desired rate.  Refer to the table on page 53 of the Reference
manual for more information.

Serial Port Speed Problems
Many computers have not been designed for the high-speed performance
requirements of the SupraFAXModem V.32bis.  Most computers work correctly
some of the time and there is no set limit at which time you will have
problems.  The main problem encountered will be data coming into the computer
faster than it can accept it, resulting in lost data.  Hardware handshaking
takes care of some of this, but sometimes the computer is so tied up with
another process that it can't even do handshaking.  With data coming in at
speeds to 57,600 bps, the computer must be very attentive to the serial port.
The following describes some things to watch for and some possible fixes:

Upload/Download Transmission Problems
If your software protocol (Y-Modem, Kermit, etc.) shows lots of blocks being
resent and Receive Error (RE) is never displayed on the modem, you are
probably losing data between the modem and computer not the phone lines.
Since the files you are transferring are probably pre-compressed, it will be
best to set your serial port close to the actual line speed.  We recommend
19,200 bps for most 9600 and 14,400 bps connections.

Faster UART Chip for PC Compatibles and External Modems
Most older and some newer PCs use the 16450 UART chip for serial
communications.  This chip was not designed for today's high speeds and has a
limited memory capacity which simply cannot keep up with faster PCs and
transmission speeds.  You can replace this chip with the 16550 UART (which
has a 16-byte buffer more suitable for high-speed transfer) if your existing
chip is socketed.  In some cases, it may  be easier for you to add a new
serial card to your system.  This may solve most lost character situations.
To find out which UART chip your system uses, consult your PC manual or
download and run the diagnostic program IS1655.ZIP from the PC file area on
the Supra BBS.

Flow Control & Hardware Handshaking Cables
This is a detail we can't emphasize enough.  Using a cable with "RTS/CTS
Hardware Handshaking" is critical if you plan to communicate at high speeds.
With error correction and data compression, the SupraFAXModem V.32bis can
often send information to the computer faster than it can accept it.  When
this happens, the computer will tell the modem to slow down.  Similarly, if a
packet is not sent correctly to the SupraFAXModem and needs to be resent, the
modem needs to be able to tell the computer to wait.  This is called "flow
control" and helps to prevent data from being lost because the computer or
modem was busy.  We recommend you enable flow control through hardware (with
a hardware handshaking cable) rather than software (using the XON and XOFF
characters) because the results are generally faster and more reliable.   If
you are using X, Y or ZModem to transfer data you must use hardware flow
control.   See Chapter 2 in the Reference Manual for more information.

One clue to a flow control-related problem will be if you are able to make a
connection but nothing else happens, or if you cannot start the
download/upload process .  If this happens, your modem is probably configured
for flow control but your cable or software does not support it.  If you are
using a Macintosh computer, it is even more likely that your cable doesn't
support hardware handshaking.  Be careful to specify this when you order a
new cable.  If you can't find them elsewhere, our sales dept. has them for
$19.95.

Multitasking
Multitasking computers are great in that they allow you to do many different
things while other operations take place in the background. Although you don't
see them in progress, those background operations can be complex and can
sometimes demand too much of your computer's attention for it to do high-speed
communications.  Transmissions will be more reliable in a single-user
situation with as few applications as possible in use.  We've identified some
specifics which can interfere with high-speed communications, depending on
your platform.  This is by no means a complete list: call the Supra BBS for
current details.

Amiga:
   Workbench 2.x allows transmission rates about 100% faster than Workbench
   1.3  which limits you to 9600 bps reliably.  Background tasks, graphics
   modes, SCSI interfaces and hard drives all can have an impact on the
   actual transmission rate.  With WB 2.x, you should be able to achieve
   reliable serial port speeds between 9600 and 19,200 bps depending on CPU
   model and speed.

Macintosh:
   AppleTalk/AppleShare (including printing) activity can lower the
   transmission rate because it has a higher priority than other serial
   communications.  Some inits may also cause problems.

PC's & Compatibles:
   Please see "Faster UART Chip"  above. TSR (terminate stay-resident)
   programs can also slow the transmission rate.

Windows:
    Windows 3.0 will often have problems at speeds higher than 19,200 bps.
    We are presently evaluating the performance of  Windows 3.1, which is
    supposed to correctly support up to 38,400 bps with 16550 UART or 486 CPU.

All Platforms - Displays:
    If you are downloading text that is displayed on your screen as it is
    received, you may have problems with your computer's display keeping up
    with the speed of the incoming data.  One way to get better performance
    is to change your display to a lower number of colors, or monochrome, so
    it is more efficient.  Whenever possible, use a file transfer protocol
    because they do not display all of the file data to the screen.

All Platforms - Processor Speed:
    Another general rule is the faster processor that your machine has, the
    better it will be for high-speed transfers.  A 68040 or 386/486 machine
    will probably do better than a 68000 or 80286.

Software Configuration / Compatibility
For the most up-to-date information on specific software settings, you'll
want to call the Supra BBS.  The final pages of this bulletin list the
programs and settings we've been able to verify, as of this printing, for
both fax and data software.

Class 2 Fax Problems
If you are having occasional problems with Class 2 fax transmissions, you may
simply need to enable software flow control (AT &K4) with you fax software.
Please  see the software configuration section for specifics.  Also, some
software better supports Class 1 than Class 2, so you may want to try
switching for best results.

Contacting Supra Corporation
For the most up-to-date information on our products and quickest help, we
recommend calling our BBS.  It contains the latest version of this bulletin
along with other useful files.  You may also find that other users have
already asked your specific question and the answer's already been posted.
It's a free service that only costs a phone call and is available 24 hours a
day!  Most questions should be answered within one work day of posting.  You
can also contact Supra via CompuServe, GEnie, BIX, America Online and
AppleLink.


Supra Corporation
7101 Supra Drive SW, Albany, OR  97321
General [phone] / Sales [phone] / Fax [phone]
Supra Tech Support  [phone]  8:00am - 5:00pm PST, M-F

Supra BBS:   [phone]  24 Hours
CompuServe      76004,565
BIX     SupraCorp
America Online SupraCorp2
GEnie   SupraTech
AppleLink      D2456