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536EX Chipset Developer’s Manual 33
Intel Confidential
Data Mode AT COMMANDS
The following sequence describes how to configure the modem for MOH to process an incoming
voice call while online. First, MOH must be enabled. The +PMH and +PCW commands are used
to enable MOH and to capture the Call Waiting tone which is sent when the voice call comes in. To
enable MOH, set +PMH=0 and +PCW=0. Next, to enable Caller ID information (optional), by
setting +VCID=1. Now the modem is configured for the incoming call. When you receive the
incoming call, the modem will get a ring indication and the software/application will issue a
+++AT to put the modem in command mode. Then, you will be prompted to either “Accept” or
“Reject” the call based on the Caller ID information (if enabled). If you reject the call, an ATO
command is issued to perform a Quick Connect to stay online. If you accept the call, the data
connection is put on hold, and the modem send a request to the server to go on hold using the
+PMHR command. The server will accept enable (1–13 returned) or reject (0 returned) the
request. If the server accepts the request to go on hold, the modem issues the +PMHF to flash the
Figure 5. Modem-on-Hold: Initiating a Voice Call in Data Mode
A9112-01
Go Back Online
(ATO)
No (Returns 0)
End Data Connection
(ATH)
Yes
Yes
(Returns 1-13)
Enable MOH
(+PMH=0)
Command Mode
(+++AT)
Request to go
on hold
(+PMHR)
Flash Hook
(+PMHF)
Flash Hook
(+PMHF)
Initiate Call
Finish Call
Disconnect
?
No
Server
Accepts
Request
?