Applies To:
  • CitectSCADA 5.20, 5.21, 5.21 Service Pack A, 5.21 Service Pack B
Summary:

The help topic "Modem Setup for Dial-up I/O Devices" is missing a modem setting which may help users resolve dial up/dial back problems and includes an incorrect modem setting for the modem at the PC end.

Solution:

It is suggested that you consult your modem manual for the exact command syntax, the modem at the PC should have DTR set to DTR always on.

On the modem at the PC end

Hayes 3COM Description
ATV1 ATV1 Enables long-form (verbose) result codes
ATQ0 ATQ0 Result codes are sent on the RS-232 connection
ATE0 ATE0 Commands that are sent from the computer are not echoed back to the RS-232 connection
AT&C1 AT&C1 DCD will follow carrier on the line
AT&K0 AT&H0 Handshaking OFF
ATW0       - Upon connection, only DTE speed is reported
AT%C0 AT&K0 Compression OFF
      - AT&B1 Fixed serial port rate
AT%E0 AT&M0 Error control disabled
AT&D0 AT&D0 DTR always on

On the modem at the I/O Device end

Hayes 3COM Description
ATV0 ATV0 Enables short-form result codes
ATQ1 ATQ1 No result codes are sent on the RS-232 connection
ATE0 ATE0 Commands that are sent from the computer are not echoed back to the RS-232 connection
AT&C1 AT&C1 DCD will follow carrier on the line
AT&K0 AT&H0 Handshaking OFF
ATW0     - Upon connection, only DTE speed is reported
AT%C0 AT&K0 Compression OFF
AT&D0 AT&D0 DTR always on
      - AT&B1 Fixed serial port rate
AT%E0 AT&M0 Error control disabled
ATS0=1 ATS0=1 Set to greater than 0 (sets the number of rings required before the modem answers an incoming call)
 
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