Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual Extended AT% Command Set

AN93

	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.
	Automatic Line Status Detection.
	After the %V1 and %V2 commands are issued, the ISOmodem automatically checks the telephone
%Vn	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.
	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
%V1	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.

80 Rev. 1.3