Specifications

Si2457/34/15/04
Rev. 1.3 33
Table 10. Extended AT% Command Set (Command Defaults in Bold)
Command Action
%$ Display AT% command settings.
%B Report blacklist. See also S42 register.
%Cn Data compression
%C0 Disable V.42bis and MNP5 data compression
%C1 Enable V.42bis in transmit and receive paths. If MNP is selected (\N2), then %C1 enables
MNP5 in transmit and receive paths.
%C2 Enable V.42bis in transmit path only.
%C3 Enable V.42bis in receive path only.
%On Answer mode.
%O1 Si2457/34/15/04 will auto-answer a call in answer mode.
%O2 Si2457/34/15/04 will auto-answer a call in originate mode.
%Vn Automatic Line Status Detection.
After the %V1 and %V2 commands are issued, the Si2457/34/15/04 will automatically check the
telephone connection for whether or not a line is present. If a line is present, the Si2457/34/15/04
will automatically check if the line is already in use. Finally, the Si2457/34/15/04 will check line status
both before going off-hook and again before dialing. %V1 uses the fixed method, and %V2 uses the
adaptive method. %V0 (default) disables this feature.
%V0 Disable automatic line-in-use detection.
%V1 Automatic Line Status Detection—Fixed Method.
Description: Before going off-hook with the ATD, ATO, or ATA commands, the Si2457/34/15/04 com-
pares the line voltage (via LVCS) to registers NOLN (U83) and LIUS (U84):
Loop Voltage
Action
0  LVCS  NOLN Report “NO LINE” and remain on-hook.
NOLN  LVCS  LIUS Report “LINE IN USE” and remain on-hook.
LIUS  LCVS Go off-hook and establish a modem connection.
Once the call has begun, the off-hook intrusion algorithm (described in "4.12.2. Off-Hook Intrusion
Detection" on page 19) operates normally. In addition, the Si2457/34/15/04 will report “NO LINE” if
the telephone line is completely disconnected. If the HOI bit (U77, bit 11) is set, “LINE IN USE” is
reported upon intrusion.