Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 80)

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80 Rev. 1.3
Table 41. 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 ISOmodem answers a call in answer mode.
%O2 ISOmodem answers a call in originate mode.
%Vn
Automatic Line Status Detection.
After the %V1 and %V2 commands are issued, the ISOmodem automatically checks the telephone
connection for whether a line is present. If a line is present, the ISOmodem automatically checks if
the line is already in use. Finally, the ISOmodem 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 ISOmodem 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 "6.6.2. Off-Hook Condition"
on page 162) operates normally. In addition, the ISOmodem reports NO LINE if the line is com-
pletely disconnected. If the HOI bit (U77, bit 11) is set, LINE IN USE is reported upon intrusion.