Multitech MMH900, User Manual

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Appendix G - MMH2834 S-Registers
I.6 Local Analog Loopback Test (Sync Mode)
This test diagnoses the connection between your MMH2834 and your
computer or terminal. In Local Analog Loopback Test mode, data entered
at the local computer or terminal are sent through the local modem’s
transmit and receive circuits (much like entering an ATU or ATU1
command in Asynchronous mode). You then compare the test characters
(multiple upper case “U” characters in Figure I-4) on your monitor with
the characters you typed. If the characters don’t match, check your
computer’s COM port setting, then verify your communication software’s
configuration.
To initiate the Local Analog Loopback Test, with the modem in
Synchronous mode:
1. Enter AT&M1U. This first switches your modem from asynchronous
to synchronous mode, and places it into the Analog Loopback/
Originate mode. The modem is now out of the Command mode and
in the pseudo On-Line mode.
2. Once you receive a connect message (if responses are enabled),
enter data from your keyboard. For this test, typing multiple upper
case "U" characters is a good way to send an alternating test pattern
of ones and zeros.
3. For a more complete test, you should also test the modem in Answer
mode. To do this, Type the Escape Sequence (+++AT<CR> or
<BREAK>AT<CR>) which brings your modem into Command mode,
while still maintaining the connection. Then type AT&M1U1 and hit
ENTER to place the modem in Analog Loopback mode, in the
Answer mode. Then repeat step 2.
Answ/Orig
Switch toggled
to Orig Position
on Power-up
UUUUU
UUUUU
Local MultiModem
Computer or Terminal
Digital Analog
Figure I-4. Local Analog Loopback Test (Synchronous Mode)