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Integrator’s Reference Manual
7-8 80-99208-1 Rev. D
Changing Data and Control Port Configuration
You may change the Data and Control port configuration at
any time, provided that the following requirements are met:
• The minimum hold time for both asserting and
de-asserting either port DTR is 10 milliseconds.
• The minimum time from asserting DTR to data
transmission is 10 milliseconds.
If these minimum times are not observed, AT command
processing may be affected. The maximum time for holding
all DTRs de-asserted is one second. If this time is exceeded,
the modem will begin its power-down sequence.
Whenever the DTR signal of the Data or Control port has
been de-asserted for a period of 10 seconds, the GSP-1620
modem shuts down the port’s RS-232 transmitter to conserve
power. This causes the port’s DSR signal to be de-asserted.
The effects of changing the port configuration are detailed in
Port Activation (DTR) Changes during Operation on page
5-15.
Control Port Signals
The Control port (CP) is an RS-232-level asynchronous
interface operating at 9600 bps using Transmit Data (TxD),
Receive Data (RxD), Data Terminal Ready (DTR), Data Set
Ready (DSR), and Signal Common (GND).
RxD and TxD perform data transfer and handshaking, while
DTR is used to turn on the modem and to let it know that
there is an application waiting to talk to it.
The Control port specifically allows dedicated usage of the
Data Port by the application. It allows all AT commands,
modem alerting, and SMS messages to be sent
simultaneously via a separate “control” port to/from the
modem. This separation of functionality is especially useful in
dormant mode, when the application and host sessions are
active, and thus the Data port appears active/in use, although
a Globalstar traffic channel is not up (no “In Call Status
Message”).