ENVIRONICS TECHNICAL BULLETIN
Contents
1. ENVIRONICS TECHNICAL BULLETIN 103 OPERATING GEN2 INSTRUMENT WITH A MODEM This bulletin describes how to operate a series 2XXX or 9100 instrument with a modem This bulletin supersedes any conflicting information in the user manual Remote Modem Configuration It is important to configure the remote modem correctly The remote modem is the one connected directly to the instrument To configure the modem connect it to a PC serial port and set the appropriate modem settings using any Terminal Emulation software such as Windows Terminal The configuration codes given are for a Practical Peripherals 9600SA and US Robotics Sportster 14 4 modem Configuration codes vary with different models and manufacturers so consult your modem s owners manual for the correct code which matches the given description data compression and error control Carrier Detect signal DCD tracks carrier AT amp C1 AT amp C1 NOTE For USR 14 4 the AT amp BO setting sets the DCE speed modem to instrument communication speed to match the speed of the modem to modem connection This requires the local modem to connect at the same speed as the instrument s baud rate typically 9600 Be sure to configure the local modem to connect ONLY at the correct speed otherwise you will not establish a connection correctly Be sure to save these settings in the modems nonvolatile RAM as indicated above Here is a typical example of modem initialization settings Note t2. but will immediately hang up if the instrument sends any data to it In order for the adapter to work correctly the DSR signal must always be asserted This is the reason for the AT amp SO0 code listed above When there is no modem to modem connection DCD is low This pulls the modems TxD line low reverse biasing diode D1 This prevents data from the instruments TxD line from reaching the modem When a connection is established DCD goes high reverse biasing D2 TxD is pulled high by DSR through R1 forward biasing D1 and allowing the data from the instrument to reach the modem TECH103 D0OC Page 2 of 2 REV 1 16AUG1996
3. hat the AT can be dropped when combining commands AT amp F reset factory defaults ATS0 1S37 98 amp Q0 amp C1 amp D0 amp KO amp SOENQ0 configure modem AT amp WO save configuration data in nonvolatile RAM AT amp YO modem uses nonvolatile RAM setting 0 when powered up TECH103 D0OC Page 1 of 2 REV 1 16AUG1996 ENVIRONICS TECHNICAL BULLETIN 103 Instrument Configuration Using the RS232 SETUP menu of the instrument set the desired communication port as follows Baud rate 9600 Terminal type VT100 Modem connected OFF yes set this to OFF Cabling Configuration The interface between the instrument and modem requires a normal modem cable straight though wiring and a special adapter This adapter is required to enable the modem to answer the phone The diagram below shows the internal wiring of the adapter This requires 2 diodes 1N914 or equiv and 1 resistor 10K ohm Wires not shown pins 1 and pins 3 25 are wired straight through Connect the adapter between the instrument and the modem with a standard modem cable TO INSTRUMENT TO MODEM 25pin female 25pin male 1N914 2 TxD TxD 2 R1 10K ohm D1 DCD 8 D2 1N914 All other lines pins 1 and 3 25 are wired straight through This adapter prevents data sent by the instrument from reaching the modem unless a modem to modem connection has been established Without the adapter the modem will attempt to answer an incoming call
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