Specifications

AN93
Rev. 0.9 45
Table 20. Extended AT% Command Set
Command Action
%$ Display AT% command settings (see text for details).
%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), %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 Si2493/57/34/15/04 answers a call in answer mode.
%O2 Si2493/57/34/15/04 answers a call in originate mode.
%Vn Automatic Line Status Detection.
After the %V1 and %V2 commands are issued, the Si2493/57/34/15/04 automatically checks the
telephone connection for whether a line is present. If a line is present, the Si2493/57/34/15/04 auto-
matically checks if the line is already in use. Finally, the Si2493/57/34/15/04 checks 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 Si2493/57/34/15/04
compares 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 "3.5.9. Intrusion Detection—
Off-Hook Condition" on page 124) operates normally. In addition, the Si2493/57/34/15/04 reports
“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.