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.

 

 

 

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Silicon Laboratories SI2493/57/34/15/04, SI2494/39 Extended AT% Command Set, Enable V.42bis in transmit and receive paths