2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

Terminal Type Specification ErrorsF-2: Garbled data at terminal screen, Double characters echoed.Line speed and/or line control parameters are inconsistent with attached device.The line control parameters the port is initialized with, must be consistent with theattached device. The IBM 7171 is shipped with the following default line controlparameters defined for all ports.Port 0 is reset to these settings when the IBM 7171 is powered on, or receives achannel reset.Seven data bits (7)Even parityOne stop bitThe 'line control parameters' must be consistent with those of the attached device.Reference the documentation (for attached device) for details on checking or modifyingthe line control parameter s.Verify that the attached device is configured for RS-232-C, asynchronous, fullduplex operation. (Half-Duplex configuration may cause double character echo foreach key depressed.) To confirm and/or modify the IBM 7171 line control parameters,refer to section 9.8, "C - Configure IBM 7171 Ports" on page 9-7 of thismanual.If no device type is specified for a terminal in Non-Volatile RAM (NV-RAM), theIBM 7171 assumes that the device is a terminal, and requests the terminal typefrom the user. If the wrong type (one that does not match the terminal) is enteredeven though it is a valid terminal type, the IBM 7171 will use the wrong TerminalDefinition Table. This will probably result in the terminal malfunctioning.To correct this situation, press the "Return to ENTER TERMINAL TYPEMessage:" key as described in "Return to 'ENTER TERMINAL TYPE:' Message"on page 3-10.If the user cannot get back to the "ENTER TERMINAL TYPE:" message viaentries at the keyboard, he must cause the IBM 7171 to restart the communicationline. This can be done for a locally attached terminal by powering the terminal off.For remotely connected lines, intervening communications equipment (modems,port selectors, etc.) may prevent proper restart when the terminal is powered onand off.Under no circumstances will the MASTER RESET function defined in section3.1.7, "Local Reset and Control Facilities" on page 3-10 be useful in recoveringfrom an incorrectly chosen terminal type table.8 -4 IBM 7171 Reference Manual and Programming Guide,