Modems - Computer Busses - page 252

echo), L2 (medium volume), M1 (speaker is off when receiving), Q1 (prohibits modem from
sending result codes to the DTE) T (set tone dial) and V1 (display result codes in a verbose
form). It can be seen that the S0 register is set to 3 which means that the modem waits for
three rings before it will automatically answer the call.
+++
AT &V
ACTIVE PROFILE:
B0 E1 L2 M1 Q1 T V1 X4 Y0 &C1 &D0 &E0 &G2 &L0 &M0 &O0 &P1 &R0 &S0 &X0 &Y1
%A000 %C1 %D1 %E1 %P0 %S0 \A3 \C0 \E0 \G0 \J0 \K5 \N6 \Q0 \T000 \V1 \X0
S00:003 S01:000 S06:004 S07:045 S08:002 S09:006 S10:014 S11:085 S12:050
S16:1FH S18:000 S21:20H S22:F6H S23:B2H S25:005 S26:001 S27:60H S28:00H
STORED PROFILE 0:
B0 E1 L2 M1 Q0 T V1 X4 Y0 &C1 &D2 &E0 &G2 &L0 &M0 &O0 &P1 &R0 &S0 &X0
%A000 %C1 %D1 %E1 %P0 %S0 \A3 \C0 \E0 \G0 \J0 \K5 \N6 \Q3 \T000 \V1 \X0
S00:000 S16:1FH S21:30H S22:F6H S23:89H S25:005 S26:001 S27:000 S28:000
STORED PROFILE 1:
B0 E0 L2 M1 Q1 T V1 X4 Y0 &C1 &D0 &E0 &G2 &L0 &M0 &O0 &P1 &R0 &S0 &X0
%A000 %C1 %D1 %E1 %P0 %S0 \A3 \C0 \E0 \G0 \J0 \K5 \N6 \Q0 \T000 \V1 \X0
S00:003 S16:1FH S21:20H S22:F6H S23:95H S25:005 S26:001 S27:096 S28:000
TELEPHONE NUMBERS:
&Z0=
&Z1=
&Z2=
&Z3=
15.8 Test modes
There are several modes associated with the modems.
15.8.1 Local analogue loopback (&T1)
In the analogue loopback test the modem connects the transmit and receive lines on its out-
put, as illustrated in Figure 15.7. This causes all transmitted characters to be received. It is
initiated with the &T1 mode. For example:
AT &Q0 <Enter>
AT S18=0 &T1 <Enter>
CONNECT 9600
Help the bridge is on fire <Enter>
+++
OK
AT &T0
OK
The initial command AT &Q0 sets the modem into an asynchronous mode (stop-start). Next
the AT S18=0 &T1 command sets the timer test time to zero (which disables any limit to the
time of the test) and &T1 sets an analogue test. The modem responds with the message
CONNECT 9600 . Then the user enters the text Help .... on fire followed by an <Enter>. Next
the user enters three + characters which puts the modem back into command mode. Finally,
the user enters AT &T0 which disables the current test.