Basic Modem Programming

Dust off your modem manual and have it handy. Use tip to connect to the modem and program the modem registers. Be sure to write out the modem's registers to NonVolatile RAM when you're done. Program the modem with the following settings.

• Hardware DTR, Normal DTR, or Reset When DTR Toggles.

  When the Sun system drops DTR, the modem should hang up the phone line and reset the modem to NonVolatile RAM settings.

• Hardware Carrier Detect or Normal Carrier Detect.

  The modem should raise Carrier Detect (known as CD or DCD) only when there is an active carrier signal on the phone connection. You'll set up the port monitor so that when CD goes active, the Sun system spawns a login.

  When carrier drops, either when the other end of the connection terminated or if the phone connection is broken, the Sun system will be notified and act appropriately. The CD signal is also used for coordinating dial-in and dial-out use on a single serial port.

• Respond with numeric result codes if this procedure is for tip's use. (Usually this is ATV0.)

  If you're setting the modem for UUCP/PPP dial-out, then program the modem to use English result codes (like CONNECT). (Usually, this is ATV1.)

  If you're using the modem for both tip and UUCP, set it up with numeric result codes, and have UUCP's chat script set it to English result codes for the duration of the UUCP connection. See the Ed Ravin out-of-print book, Using and Managing UUCP, for the nitty-gritties.

• Send basic result codes only.

  tip only wants to see result codes 0 through 4. If it sees other result codes, it calls them an error. (Sometimes this is ATX0 or ATQ0.)

• Do not echo commands. (Usually this is ATE0.)

• Modem is locked at a single-speed setting between the Sun system and the modem.

  The speed may vary as needed between local and remote modem, but should remain constant between the Sun system and the modem. (If your modem can't do this, use it for a paperweight and buy one that allows split speeds If your boss won't let you do this, OK, but you should whine loudly.)

• If this modem is used for dial-in, turn on Auto-Answer. (Sometimes, this is ATS0=1.) If the modem is not used for dial-in, turn off Auto-Answer. (Sometimes, this is ATS0=0.)

• Set the modem to your parity and word-length requirements. Use 8 bits, no parity if you can.

• Set the modem to your flow control scheme. Use hardware flow control (CTS/RTS) if you can, software flow control (XON/XOFF) if you must, or no flow control if you just have to.

Useful Modem Register Settings

The USR Courier V.34 and Telebit WorldBlazer modem settings are our own work. The USR V.Everything settings are courtesy of Doug Hughes at Auburn University. These settings have worked well in bidirectional, interactive dial-in, UUCP, and PPP applications. Other modem settings can be found at the following URL.

http://www.stokely.com/unix.serial.port.resources/modem.mfg.reg.isdn.html

It will probably take a few tries to get all the right settings into your modem. No, you don't need to set all the S registers this way. These have been tweaked for the client's application. Your mileage will definitely vary, but the entries below on these modems, from the B0 (or B1) C1 through the S00=001 are very good ones to use, IMHO.

USRobotics Courier V.32bis V.34 Fax Settings

B0  C1  E1  F1  M1  Q2  V0  X0
BAUD=38400  PARITY=N  WORDLEN=8
DIAL=TONE   ON HOOK   TIMER
&A0  &B1  &C1  &D2  &G0  &H1  &I0  &K1  &L0  &m4  &N0
&P0  &R1  &S0  &T5  &X0  &Y1  %N6
S00=001  S01=000  S02=255  S03=013  S04=010  S05=008  S06=002  S07=060
S08=002  S09=006  S10=007  S11=070  S12=255  S13=000  S14=000  S15=000
S16=000  S17=000  S18=000  S19=000  S20=000  S21=010  S22=017  S23=019
S24=150  S25=005  S26=001  S27=000  S28=008  S29=020  S30=000  S31=000
S32=009  S33=000  S34=000  S35=000  S36=000  S37=000  S38=000  S39=000
S40=000  S41=000  S42=126  S43=200  S44=015  S45=000  S46=000  S47=000
S48=000  S49=000  S50=000  S51=000  S52=000  S53=000  S54=064  S55=000
S56=000  S57=000

Dip Switches: (UP = dip switch up, DN = dip switch down).

Table 132 lists the dip switch settings for the USRobotics Courier V.32.

USRobotics Courier V.Everything Settings

B0  C1  E1  F1  M1  Q0  V1  X7
BAUD=115200 PARITY=N  WORDLEN=8
DIAL=HUNT   ON HOOK   TIMER

&A3  &B1  &C1  &D2  &G0  &H1  &I0  &K3  &L0  &m4  &N0
&P0  &R2  &S0  &T5  &X0  &Y1  %N6  #CID=0 
S00=003  S01=000  S02=043  S03=013  S04=010  S05=008  S06=002  S07=060
S08=002  S09=006  S10=007  S11=070  S12=050  S13=000  S14=001  S15=000
S16=000  S17=000  S18=000  S19=000  S20=000  S21=010  S22=017  S23=019
S24=150  S25=005  S26=001  S27=000  S28=008  S29=020  S30=000  S31=000
S32=005  S33=000  S34=000  S35=000  S36=000  S37=000  S38=000  S39=000
S40=000  S41=000  S42=126  S43=200  S44=015  S45=000  S46=000  S47=000
S48=000  S49=000  S50=000  S51=001  S52=000  S53=000  S54=064  S55=000
S56=000  S57=000  S58=000  S59=000  S60=000  S61=000  S62=000  S63=000
S64=000  S65=000  S66=000  S67=000  S68=000  S69=000  S70=000

3. Telebit WorldBlazer Settings

   B1  E1  L1  M0  Q2  T   V0  X0  Y0 
   &C1 &D3 &G0 &J0 &L0 &Q0 &R3 &S4 &T4 &X0 
   S000=1   S001=0   S002=43  S003=13  S004=10  S005=8   S006=2   S007:90 
   S008=2   S009=6   S010=14  S011=70  S012:255 S018=0   S025=5   S026=1  
   S038=0   S041:1   S045=0   S046=0   S047=4   S048=0   S050=0   S051:253
   S056=17  S057=19  S058:2   S059:15  S060=0   S061:0   S062=15  S063=0  
   S064:1   S068=255 S069=0   S090=0   S092:1   S093=8   S094=1   S100=0  
   S104=0   S105=1   S111:30  S112=1   S151=4   S155=0   S180=2   S181=1  
   S183=25  S190=1   S191:6   S253=10  S254=1   S255=255