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Integrator’s Reference Manual
5-10 80-99208-1 Rev. D
Table 5-3. Port Arbitration Behavior
Control
Port Active
Data Port
Active
Port Behavior
No No Control and Data ports are inactive and modem is powered
down unless the Diagnostic port is active.
No Yes The Data port processes all data and AT commands,
including the following:
■ Online-Command mode is supported on the Data port.
■ All port configuration commands apply to the Data port
as defined in Port(s) Affected by AT Commands on page
5-13.
■ If a non-data call (e.g., Markov, Loopback) is already
active when a call is attempted with the ATD command,
the BUSY result is returned. If a data call is active, a NO
DIALTONE result is returned.
■ DTR cannot be used to terminate a call or enter
Online-Command state (AT&D2 or AT&D1
configurations), unless the Diagnostic port is active.
Note: This is because the modem powers down if all
DTRs are low. DTR can be used to terminate the call or
enter Online-Command mode, although the modem will
power down after approximately 1 second.
Yes No All AT commands are processed on the Control port. Data
calls are not supported because the Data port is inactive.
■ All data calls initiated using the ATD command return
NO DIALTONE.
■ ATD<phone number> returns NO DIALTONE.
■ The ATD command with #627568 (Markov test call) or
#56672225 (Loopback test call) dial strings initiates a
call if a call is not already active. If a call is already
active when the call is attempted, a BUSY 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.
■ The online escape sequence “+++” surrounded by guard
time is ignored.
■ Online-Command mode command ATH returns OK.
ATH will terminate an active test call.
■ Online-Command ATO returns NO CARRIER.