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Developing Modem Applications
80-99208-1 Rev. D 5-11
Yes Yes All AT commands are processed on the Control port. The
Data port is used only for the transfer of packet or
asynchronous data resulting from a data call.
AT commands received on the Data port are ignored.
■ A packet data call can be initiated on the Data port by
sending a PPP packet; for details, see Packet No Dial
($QCPKND) on page 6-50.
■ ATD#777 received on the Control port initiates a packet
data call on the Data port. If a non-data call (e.g.,
Markov, Loopback) is already active when the call is
attempted, a BUSY result is returned. If a data call is
active, an ERROR result is returned.
■ ATD<phone number> received on the Control port
initiates an asynchronous data call on the Data port.
If a non-data call (e.g., Markov, Loopback) is already
active when the call is attempted, a BUSY result is
returned. If a data call is active, an ERROR result is
returned.
■ The ATD command received on the Control port with
#627568 (Markov test call) or #56672225 (Loopback
test call) dial strings initiate a call if a call is not already
active. If a non-data call is already active when the call
is attempted, a BUSY result is returned. If a data call is
active, an ERROR result is returned.
■ Port configuration commands apply to the Data port
and Control port as defined in Port(s) Affected by AT
Commands on page 5-13.
■ Online-Command mode is not supported on the Data
port.
■ The online escape sequence “+++” surrounded by guard
time is ignored on both ports.
■ ATH received on the Control port terminates an active
data call or special test call. It returns OK whether or not
a call is active.
■ ATO received on the Control port returns OK if a call is
active; otherwise, it returns NO CARRIER.
Table 5-3. Port Arbitration Behavior (continued)
Control
Port Active
Data Port
Active
Port Behavior