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Entry type: FAQ Entry ID: 23806944, Entry date: 10/18/2006

What options exist for doing a test without modems using a zero modem cable?

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Configuration notes:
You can make a direct connection between two TIM modules without a modem using a zero modem cable.
This can be used to connect dedicated-line TIMs to the RS232 port, such as the two TIM 3V-IE versions and all TIM 4 types.

Direct connection using a zero modem cable enables the principle communication function between two TIMs to be tested independent of the modem transmission link. The modems can be incorporated into the connection later on with the correct settings, and transmission can be tested.

"Dedicated line" mode must be selected for data exchange between two TIMs (polling, polling with a time slot or multi-master polling). A dial-up mode cannot be simulated via the zero modem cable because this mode only works in conjunction with a dial-up modem.

The zero modem cable required is available through the SIMATIC NET catalog, order number 6NH7701-0AR.


  • Only point-to-point connections are possible for a direct connection between two TIMs via a zero modem cable.
  • Duplex and half duplex connections are possible.
  • The parameters of the TIMs should be set as they would be with a dedicated line or wireless modem connected. The control of the modem via RTS and check-back via CTS can be simulated with the cable because both signals are bridged in the cable.
  • The zero modem cable may not exceed 15 m in length.
    The cable which is available to order is 6 m long.

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