Computer News 80

Open forum for users of the TRS-80 Model I/III/4 computers. Post questions, and answers. Post items for sale.

My Photo
Location: Casper, Wyoming, United States

Saturday, December 24, 2005

Using the Model 4 on the Internet

by Ed Henderson

(Reprinted from Volume 8 Number 6.)

After playing around on the local B.B.S.'s with a 2400 baud Zoom modem for some months now, I got restless - no, bored waiting for things to come down to me on my trusty old Model 4. A call or two to Stan and Ron soon fixed my dilema. I bought a new 19200 baud Zoom modem and got an early copy of David Goben's patch for XT4 ver. 1.8.7a. Applied the patch, booted-up the new modem, and WONDER OF WONDERS, I was out there just smokin'!

Now, I'm out there in cyberspace sending and receiving at warp speed. I mean WARP SPEED. As many of you know, using capitol letters during transmissions on the Internet is like yelling at someone. Well, that's what you feel like doing when you go from 2400 baud to 19200 baud. It may sound impossible, but this patch works. I found a small bug, but have worked around it very easily.

When my Model 4 tells me I've connected at 19200, I immediately hit one or two capitol Oh's (not zero, the letter "O"). This has kept the computer from switching to the XT4 menu, like when you hit the key from within the program. If the menu does come up, at any time during your session with a B.B.S. or the Internet, just hit and you are back the where you want to be - at 19200 baud on the Information Highway.

Of course, before you can utilize David's patch you must setup your computer and XT4 to recognize the speed of the modem. From the XT4 menu, select "I" to initialize your modem. When the selections for baud rate come up, just hit the number "7", and the new baud rate will be recognized. When you are in the dialing directory, you must tell the computer to recognize the new baud rate. This is done by hitting the "U" key to update your directory entries, and then hit the number of the B.B.S. or on-line service you wish to update. When it asks you what baud rate, proudly hit the number "7" again. And, when all is done, you will be "out there" at 19200 baud.

One small problem is that many B.B.S.'s and online services do not yet have modems that support the higher baud rates. Some are only 2400, while others may be running at 9600 or 14,400. In any event, you will be able to run up to 19,200 depending on the other end of the line. It is very exciting when you first hook-up at the higher speeds. Things just seem to jump onto the Model 4 screen, instead of slowly
>scrolling by in front of you.

When downloading files, I have found that they do not run at the highest possible baud rate. For example, a program that took almost 5 minutes on the old 2400 baud modem now takes about 2 minutes. This is probably due to the internal time it takes the Model 4 to get, sort, check and store the information on my hard drive. I have not yet figured out how to make the Model 4, running under the patched XT4, to download in other than "X" modem protocol. "Z-Modem" seemed to work fastest on the old XT I have - running at 2400 baud. It probably saves about 10% of the downloading time as opposed to using the "X" modem protocol. I have downloaded the same stuff just to test the difference between the protocols available on the IBM XT, so I know that under "Z-Modem" it's faster and more reliable than "X-Modem" protocol.

Even though you can't yet get the full speed when downloading with a new 19,200 baud modem, 2 minutes compared to what used to take 5 minutes is still 2 1/2 times faster (250%) at the least. Think of the time savings you can realize with a new modem and a patched XT4 program. It must be XT4 version 1.8.7a, though. It does not work on any other version of XT4. After patching the correct version of XT4, I used REMOVE to rid my hard drive of the original XT4, and then used RENAME to call XT4V187A just plain XT4. The XT4/DAT file still worked fine with the above changes to the dialing directory.

One last note. When you setup the dialing directory, use "*70W" BEFORE the phone numbers in your directory if you have the Call Waiting feature on your phone line. Nothing is worse than getting near the end of a download or upload file and having someone call in on the Call Waiting line. "ALL IS
LOST!" if you don't have the "*70W" typed-in before the dialed number.

HAPPY SURFIN' with David Goben's patch for XT4V187A and a new 19,200 Zoom modem from CN 80. Oh, my wife wants the other wifes out there to know that all of this DID NOT cut down on the time that I am "lost" in cyberspace. All it did was make that time much, much more productive for me. Well, you can't have everything, can you?
-Ed Henderson

(Reprinted from Computer News 80 JUNE 1996 VOLUME 9 NUMBER 6)

by David Goben

To answer all those questions many of you have about high speed data communications: Yes, you can use a 19,200 Baud rate. And yes, this is supported by the 14,400 Baud external modems currently on the market. The problem is, none of the Model III/4 communications packages openly support it. Why not? Because at the time of their release no modems supported speed of over 9600 Baud. The serial interface inside the Model III/4 is capable of supporting Baud rates from 50 through 19,200. It cannot go higher than this because you would need a 16-bit port, and that's kind of tough on an 8-bit machine. The good news is, you WILL have the knowledge required to communicate at 19,200 Baud on a Model 4 after reading this column.

First things first. How do you set your baud rates? That's relatively easy. First you must load your communications driver, COM/DVR. Do this from the DOS Ready prompt by entering SET *CL COM. This defines a device called *CL for serial communications. The next step is to set you

communications parameters via the SETCOM command. You can do this by entering SETCOM (Q). You will be prompted for all settings: Baud, word length (7 or 8 bit word length), Stop bits (1 or 0), Parity (EVEN, ODD, or OFF), Break (usually 3 for CTRL-C), and other settings. You can select defaults by simply pressing the ENTER key. Most communications program, such as Bill Andrus' XT4 for the Model 4 have their own communications drivers built right into them, so you don't have to worry about using the SET command. For example, if you are developing your own program that will have a communications driver in it, you can set up really fast using the following simple assembly language code:

LD A,101
OUT (0E8),A
OUT (0E9H),A
LD (INTVC$+5*2),HL
SET 5,(IY+22)
LD A,(IY+22)
OUT (0E0),A

This code first points the IY index register to the system's internal flags area. It then resets the serial RS-232C by sending any value in register A to port E8. We then send the code to set the 19,200 Baud rate to port E9. Next we set no-parity, no break, 1 stop bit, and an 8-bit word code to port EA. Finally, we set out communications driver to HL, stuff it into the proper vector, then set the flag that will activate this vector for system scrutiny. The baud rate is actually set up, for whatever reasons, in two parts of the same byte. You must tell the system at what baud rate to send information, and at what baud rate to receive it. I have never seen a system that would use a different sending and receiving rate, but I suppose that somewhere there is a good reason for this. Anyway, to send out this code, we take the baud code and place it in the high nibble (upper 4 bits) and low nibble (lower 4 bits) if the byte (do you like these bona-fide technical terms?). Thus, to send a rate of 19,200, we would be using the code F (15 decimal) in the high and low nibbles, and so the full byte code would be FF. Check with a technical reference manual if you are interested in what codes correspond to what ates. If we get enough queries, they will be
published here.

>XT4 AT 19,200 BAUD
Anyway, while checking the background for writing this little treatise, I discovered that XT4 (mentioned earlier) did have support for 19,200 Baud already built right into it, but it was simply disabled. To enable it under XT4 version 1.8.7a, which CN80 currently distributes through the File Cabinet and I believe with orders for modems, you have to install one simple patch:

PATCH XT4 (D1C,D2=07:F1C,D2=06)

REMEMBER, apply this patch ONLY to XT4 version 1.8.7a. It will not work with older versions! Notice that when you select "Initialize RS-232-C" from the menu (I), the 7th selection, 19200 will not be shown, simply because the text for the menu was never inserted. If you would LIKE to insert it, apply the following patch. Notice that the last 2 lines of the patch ALSO INCLUDE the above patch. Create the patch by typing BUILD XT4/FIX and pressing the ENTER key, then type in the following lines:

.Patch Xt4 version 1.8.7a for 19200 baud
.David Goben. April 1995
D05,AA=20 72 61 74 65 3A
F05,AA=3A 20 20 5B 31 5D
D05,B0=20 31 3D 33 30 30 2C 20
F05,B0=3D 33 30 30 2C 20 5B 32
D05,B8=32 3D 36 30 30 2C 20 33
F05,B8=5D 3D 36 30 30 2C 20 5B
D05,C0=3D 31 32 30 30 2C 20 34
F05,C0=33 5D 3D 31 32 30 30 2C
D05,C8=3D 32 34 30 30 2C 20 35
F05,C8=20 5B 34 5D 3D 32 34 30
D05,D0=3D 34 38 30 30 2C 20 36
F05,D0=30 2C 20 5B 35 5D 3D 34
D05,D8=3D 39 36 30 30 2C 20 37
F05,D8=38 30 30 2C 20 5B 36 5D
D05,E0=3D 31 39 32 30 30
F05,E0=3D 39 36 30 30 1F

Press BREAK to stop building the file, then apply the patch to a backup copy of XT4/CMD by using the command PATCH XT4/XT4. Finally, notice that the patch program will report 9 patch lines installed. This is because the actual patch lines are those starting with the letter D, and those lines beginning with F are simply checks, testing the file for the data that the new patch lines will overwrite. Regardless of whether you typed in the short patch or the long patch, when you select [I] to initialize the RS-232-C, type the digit 7 to select the 19200 baud rate. This will bring you up to speed.
You can find the Computer News 80 on a CD disk at our Computer Store at:


Blogger MrSnerg said...

I have never used XT4, I used FastTermII. I ended up not going for anything more that 9600 because with vt100 emulation it would lose characters at 19,200. Did you have any issues with character loss? File transfer worked fine.

3:59 PM  

Post a Comment

<< Home