PC adapter FLL222


This adapter allows a PC with two serial ports to non-intrusively monitor a 9-way RS232 interface connection.

It is designed for use with our FSA32 PC based serial data analyser when running on a PC with two serial COM ports, but is also suitable for other similar applications.

  • Allows a PC with two serial ports to non-intrusively monitor a 9-way RS232 interface
  • Works by connecting signal lines 2 (9-way RD) and 3 (9-way TD) to two separate DB9 female connectors (click here for circuit)
  • Designed for use with our FSA32 PC based analyser running on a PC with two COM ports
  • Allows a PC application which can handle two COM ports to view full-duplex data
  • May be used for 25-way interfaces, if 9/25 way converters are used

Further information

For PC's with one COM port, one of our FLL221 PC adapters may be more suitable (click here).

This adapter does not allow the PC to transmit back to line, nor to monitor control lines, for that see our FLLBOB adapter (click here).

 What's included

FLL222 adapter, 12 months warranty, lifetime support by phone or email

Order code:  FLL222  79.00 + VAT (UK) Discontinued  

 Application notes

The benefits of using two serial COM ports when using a PC based serial data analyser

When attempting to non-intrusively monitor the signals on an RS232 interface lead, a problem arises if the monitoring PC has only one COM port. This is because an RS232 interface lead carries two serial data signals, (RD on line 2 and TD on line 3 if 9-way) but a PC serial COM port has only one input, its own RD line on position 2.

The problem can be solved by using a PC with two serial COM ports, and an adapter such as the FLL222 (provided the PC application program can handle both COM ports at once).

This allows the user to monitor data occurring on both RD and TD lines simultaneously, as can happen during "full-duplex" working.



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                       New Forest Electronics Tel. +44 (0) 1425 650089                 Issue 3.110    11 June 2024