User's Manual

Company Confidential 38 Raveon Technologies Corp.
button. This will force the modem into the Command Mode, as well as set the serial port to 9600
baud, 8 data bits, one stop, and no parity. If the baud-rate was OK, verify the AT, BT and CT
times, that they are long enough for you to enter the +++ string.
Symptom: Long delay before transmitting
Solution #1. Verify that serial port timeout is OK. The ATR3 command sets the number of
milliseconds that the M8S will look for in the serial input data stream. If a pause greater than this
value happens, the modem will transmit. If the ATG0 parameter is set very large, say 2000, this
means 2 seconds, and the modem may simply be waiting a long time. Typical settings for this
parameter are 20 (20mS).
Symptom: Cannot enter Command Mode
Solution #1. Verify the serial port baud rate. This is difficult if it is set wrong, because you
cannot enter the command mode to check it. Try all possible baud rates, and see if one of them
works with the modem. Alternately, remove the rear cover of the modem, and press the CONFIG
button. This will force the modem into the Command Mode, as well as set the serial port to 9600
baud, 8 data bits, one stop, and no parity. If the baud-rate was OK, verify the AT, BT and CT
times, that they are long enough for you to enter the +++ string.
Solution #2. Handshaking. You may have hardware handshaking enabled on your terminal
program, but the hardware or cable may not support it. Disable hardware handshaking on your
terminal program to verify this is the issue.
Symptom: Modem appears dead.
Solution #1. Verify the power is on. When the modem has good DC power, the PWR LED
will blink once per second. If it is not blinking, either the modem does not have power, the
modem is broken, or the LEDs have been disabled via the ATL0 command.
Solution #2. Verify Low Power Mode. The M8S has an optional Low Power Mode (LPM). If
LPM is enabled, the M8S will power down whenever the DTR line of the serial port is turned off.
The Power LED will blink once every 10 seconds in the LPM mode. The ATSM command is
used to set or read the Low Power Mode. ATSM 1 enables it, and ATSM 0 disables it. If LPM is
used (ATSM 1), then the M8S will turn off when the DTR line is off, or the program connected to
the serial port is closed, or the RS-232 connector is un plugged.