AT&T DataPort PCX Modem User Manual page 56

AT Commands and S-Registers
Table B-1. AT Command and S-Register List (17 of 21)
AT Command/
S-Register
&Q n
&R n
&S n
Description
ASYNC/SYNC MODE AND COMPUTER DIALER
TYPE
Determines the DTR operating mode. &Q is an
extension of the &M command. &Q1, &Q2, and &Q3
are for the serial interfaced (external) modem only.
&Q, &Q0 Enables direct asynchronous operation.
&Q1 Enables synchronous Connect mode with
asynchronous offline Command mode.
&Q2 Enables synchronous Connect mode with
asynchronous offline Command mode, and
enables DTR dialing of directory slot 0.
&Q3 Enables synchronous Connect mode, and
allows DTR to act as a talk/data switch. A
call is manually initiated when DTR is
inactive. When DTR becomes active,
handshaking proceeds in originate or
answer mode (depending on modem state).
&Q5 Enables asynchronous operation in
Error Control mode.
&Q6 Enables asynchronous operation in
normal mode (speed buffering).
RTS/CTS ACTION
Determines the handling of the CTS (Clear To Send)
signal relative to the RTS (Request To Send) signal.
&R, &R0 In synchronous mode, CTS tracks the state
of RTS. S26 defines the RTS to CTS delay.
&R1 In synchronous mode, treats CTS as
always ON; RTS transitions are ignored.
DSR CONTROL
Determines the handling of the DSR (Data Set
Ready) signal.
&S, &S0 Forced On.
&S1 DSR becomes active after answer tone is
detected, and inactive after the carrier is
lost.
Issue 2 July 1995
B-17