Multi Tech Equipment MTA128ST - Manual (Page 37)

Troubleshooting
37
When using X.75 data protocol to transfer data via the Zmodem, the Zmodem displays Intermittent bad
packet errors and data throughput drops.
This occurs in cases when the X.75 packet size is greater than 1024 bytes and the terminal adapter
sending the file has a fast serial baud rate (e.g., 115200 bps) and the terminal adapter receiving the file
has a slow serial baud rate (e.g., 19200 bps). To reduce or possibly eliminate this, reduce the X.75 packet size
(S53) to a value less than or equal to 102 bytes (e.g., ATS53=512). However, if you set the receiving terminal
adapter’s serial baud rate nearly equal to or greater than the serial baud rate of the sending terminal
adapter, then the packet size can be greater than 1024, and Zmodem transfers the data without
bad packet
errors.
The MTA128ST/NT won’t accept V.120 calls from a 3Com Impact IQ terminal adapter. The Impact IQ
displays a connected status, but the MTA128ST/NT does not.
The MTA128ST/NT is looking for a SABME command from the Impact IQ to finish establishing the V.120
connection. However, the Impact IQ won’t send a SABME until it has data to send. Have the Impact IQ
send a character by pressing any key (such as the space bar) on the terminal attached to the Impact IQ. The
MTA128ST/NT responds with a CONNECT message and displays the key you pressed (e.g., a space).
MTA128ST/NT receives garbage characters when connected to a 3Com Impact IQ terminal adapter.
Most likely, the Impact IQ has compression turned on. The compression used by the Impact IQ is
incompatible with the compression used by the MTA1 28ST/NT. Disconnect the data connection and give
the Impact IQ the command AT%CO and then establish the data connection again. The garbage
characters should disappear.
The MTA128ST/NT receives garbage characters after receiving several good characters when connected
to a 3Com Son ix adapter.
Most likely, the Sonix has compression turned on. The compression used by the Sonix is incompatible with
the compression used by the MTA1 28ST/NT. Disconnect the data connection and the give the Sonix the
command AT”HO (that’s a double quote) and then establish the data connection again. The garbage
characters should disappear.
Each time a 3Com Sonix terminal adapter originates a V.120 call, the MTA128ST answers the call as a
V.110 call.
The Sonix sends V.1 10 information in the SETUP message to the network. Since the MTA128ST’s default
is with Auto Protocol Detection enabled (ATS52=1), it looks at SETUP information from the Sonix and
determines erroneously that it is a V.1 10 call. Disable Auto Protocol Detection in the MTA128ST with the
command ATS52=0 and try the connection again.
The MTA128ST/NT won’t connect to an ELSA terminal adapter with the V.120 data protocol.
Most likely, the ELSA terminal adapter has compression turned on. The compression used by the ELSA
terminal adapter is incompatible with compression used by the MTA128ST/NT. Give the ELSA the
command AT%CO to disable compression and try again.
Apple Macintosh Compatibility
The IWay Hopper works with all Macintosh models with a serial port. Some models may require a USB-to-
serial adapter since the MTA1 28ST/NT is a serial RS-232 device. Scripts are provided for Mac OS 8
through Mac OS X. These scripts also work with Mac OS 7.x with the Apple Internet Connection Kit
installed. (OS 8 and 8.1 have the Apple Internet Connection Kit built-in and Mac OS 8.5 through Mac OS X
have Internet connection capabilities built-in.) If you don’t use the Internet connection abilities provided by the
Mac OS, then you will need to create your own initialization string to suit your needs. Generally, these
initialization strings can be based on the Factory Profile command &Fn to set up the desired protocol.