User`s guide

Troubleshooting
A Host/Modem - ModemISLTA-10 Adapter configuration has many user-selected options
including the choice of modems, configuration of the modems, the operating system of the
host, the network interface link protocol, and the serial bit rates of both the host/modem
link layer and the SLTA-10 Adapter modem link layer.
The most common problem is a failure to use the correct SLTA-10 Null Modem
Cable specified in Chapter 3.
SLTA- 70 Adapter and Modem Do Not Answer or Pick Up
The modem attached to the SLTA-10 Adapter must be configured to auto-answer if you
want it to pick up and connect when dialed up. Set the modem’s SO register to a non-zero
value.
Modems Will Not Connect
This is an unusual case with current modems which utilize modulation scheme fallbacks
and error control negotiation fallbacks. One rule for modem modulation speed
configuration is that if your modem can be configured to connect at the speed of the last
‘AT’ command, do so. Also, be sure that the modem’s connect/carrier (Register S7) wait
time is sufficient. Start with 60 seconds.
SLTA- 70 Adapter to Host Link Fails Completely
This can be observed as repeated retries at the link layer when the first actual downlink
or uplink transfer is attempted. This can be due to any of the following conditions (in
order of likelihood):
l Mismatched network interface link protocols. One end is using the ALERT/ACK link
protocol and another is using the buffered link protocol. These settings are
determined on the SLTA-10 Adapter by Switchl/CFGS and in the host by network
driver switches. The ALERT/ACK link protocol should be used (OFF/down position
for SwitchlICFG3 on the SLTA-10 Adapter).
l Using the Host Connect Utility in the wrong network interface link protocol. HCU
can and may modify the current configuration of the DOS network driver. Ensure
that the command line switches for the HCU maintain the desired network interface
link protocol and serial bit rate settings. For example, you may have used the /N
option with the DOS device driver, but did not use the -N switch with HCU.
l Using XON/XOFF flow control in your modem. Since the SLTA-10 Adapter network
interface protocol is a binary one, this configuration will interfere with, or lock up,
your modem. Be sure that this feature is disabled in your modems.
14-2
Modem Troubleshooting