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 (503) 967-2444. 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 (503) 967-2400 / Sales (503) 967-2410 / Fax (503) 967-2401 Supra Tech Support (503) 967-2440 8:00am - 5:00pm PST, M-F Supra BBS: (503) 967-2444 24 Hours CompuServe 76004,565 BIX SupraCorp America Online SupraCorp2 GEnie SupraTech AppleLink D2456