Saia-Burgess
Controls Ltd.
Manual Modem PCDxx7 Serie│Doc. 26/793; Ed. E2│30.04.2005
Modem parameters and Main Driver functions
2
2-7
Main Driver function
Incoming call
When the Driver is in the WAITING
status, an incoming call is detected
by the modem message “RING”. At
this point the Driver switch to the
status “INCOMING CALL” and the
Start call are not possible anymore.
The Driver is waiting now for a new
“RING” message from the modem
or the message “CONNECT”, if this
one doesn’t append in a configured
time, the Driver is going back to the
“WAITING” status.
If the modem get synchronized, the
message “CONNECT” is detected
by the Driver and this one will
change status to “INCOMING CALL
CONNECTED”. The output signal
of the function “CONNECT” and
“INCOMING” are set to 1.
In this status the Driver will not
watch anymore what is going or
coming through the serial line. For
this reason it is possible now to use
the serial line with any other kind of
protocol. The Driver is just watching
the status of the DCD signal.
When the DCD signal disappears, it means the phone connection is lost or the mo-
dem can’t synchronize anymore, this could append any time and the status of the
serial line will be unknown.
So the modem and the serial line have to be totally reconfigured. The Driver goes in
the “STARTING” status.
DRIVER
is in waiting status
First RING is
detected
(incoming call)
The DRIVER goes in incoming call status
1) Disable the possibility to start call
2) wait for the CONNECT status of the modem
3) wait for RING signal from modem in a delay of time
CONNECT
signal arrived
from the modem
The DRIVER is in
incoming connected
1) Output signal
CONNECT and
INCOMING are set to
TRUE
2) Waiting for a lost of
DCD signal
No signal
CONNECT or
RING came in
the DELAY
DRIVER go back in the
status READY and
WAITING
DCD signal is
lost
The DRIVER goes
in initialization
1) The START_Flag
is reset
