Having problems with DOOM 1.2 serial?  I tried several modems and
configurations.  The below string seemed to provide the most 
consistent results across the widest number of modems.

AT &F S46=0 &K0 &Q0 &D2 &W
AT Z H0


Line 1 is the initialization string, which does the following:

&F    - This fetches the factory default in most modems.  Always a
        good starting point.

S46=0 - This register setting disables compression on many v.32 and v.42
        modems.  You might also try S46=136 or %C0.

&K0   - Disable flow control between the modem (DCE) and your PC (DTE).
        This was one of the most common problems -- You should look
        at flow control options more closely if you connect and just hang
        WITHOUT the screen clearing and displaying the blue banner.  Check
        your modem documentation carefully.  The command(s) to manipulate
        flow control varies quite a bit on various modems.

&Q0   - Places the modem in DIRECT mode.  This is by far the best method
        for pumping data down those wires!  Stay away from the error
        correcting and speed buffering configurations.

&D2   - DTR handling.  DTR is the signal (voltage) on the serial connector
        on your PC that says "I'm here".  This control helps with initially
        talking to the modem and disconnecting.  The &D2 in tells the modem
        how to handle the loss of the DTR signal from the PC.  In this case,
        the modem will go into COMMAND MODE from DATA MODE (if not already
        there) and send the normal verbose response (i.e. "OK").

&W    - Write the configuration to the modem's memory.  This is optional
        but I always like to do this -- just like I always like to use
        the factory reset (&F) at the beginning.  

        IMPORTANT:  When you use the &W your permanently change your modem
                    modem settings.  If your other communication programs
                    do not set your modem each time, you may have to 
                    configure your modem for those other programs again.


An alternate configuration:

Another common problem I found on the 14.4 flavor modems was the tendency
for some of these to report a 14.4 CONNECT on one side, and a 9600 on the
other.  Every modem has a method for forcing a connect speed.  The most
common I found is on register S37.  The following init string usually fixed
the problem:

AT &F S46=0 &K0 &Q0 &D2 S37=F8 &W
AT Z H0

Which does the following:

&F      - as described above.

S46=0   - as described above.

&K0     - as described above.

&Q0     - as described above.

&D2     - as described above.

S37=F8  - Forces the modem to 9600 bps.  F8 is hexadecimal notation.  Your  
          modem documentation may describe the settings in decimal or 
          in binary notation.  For example:

          F8        - hexadecimal
          248       - decimal
          11111000  - binary

          The binary notation is the most clear when interpreting the 
          effect to bit registers.  Once you set your bits correctly,
          you can use the calculator in Windows 3.1 to binary/hex/decimal
          conversions (when in the scientific mode).
          
          Keep in mind the place holders and the least to most significant
          bits!  It's easy to work in the wrong direction when dealing
          with bit registers.  

          If binary notation is foreign to you, call your modem vendor
          and describe what you need.  They will be able to give you the
          proper code.

I also tried the following init strings with varying degrees of success
depending on the modem: 

AT&Fs46=0&Q0&D2&W
AT&F%C0&D2&W
AT&F&Q0%C0&D2&W
AT &F S46=0 S48=0 S23=187 &Q0 &D2 \J0 &W
AT&F S46=0 &Q0 &D2 S37=F8 %C0 &W
AT&F S46=0 S48=0 &Q0 &D2 S37=F8 %C0 &W
AT&FE0V1X0S46=0&Q0&D2&W


I hope this helps you frustrated serial players out there.

Finally, thanks to ID for the most awesome games I've played.  Wolf3D,
SPEAR, and DOOM have provided the best value for my money.  I urge you
to register your software to help support them!


Keith Turbyfill
Compuserve ID: 73322,332
America On Line ID: turby
Internet ID: turby@aol.com