Envoy Application Programming Manual

Asynchronous Line Supervisor Protocol
Envoy Application Programming Manual—427159-001
10-20
CONTROL 17 Procedure (Automatic Speed
Detection)
Example 10-5 shows how to define a continuous break:
CONTROL 17 Procedure (Automatic Speed Detection)
The CONTROL 17 procedure must be used to enable the connection for the automatic
speed-detect feature. When CONTROL 17 is issued, the line driver sets the speed to 300
baud and raises the data terminal ready (DTR) signal. When the sending station detects
the data set ready (DSR) signal, it raises the request to send (RTS) signal and waits for
up to 30 seconds for the clear to send (CTS) signal. If CTS is not detected, a modem
error is returned to the application process. If CTS is detected, the driver waits for up to
30 milliseconds for secondary carrier (SCF). If SCF is detected, the driver changes the
line speed to 1200 baud.
Line-Error Handling
The figures in this subsection show the Envoy line-error handling during READ and
WRITE operations.
Figure 10-3
on page 10-21 shows the action of the supervisor station in response to line
conditions on a READ operation.
Example 10-5. Define a Noncontinuous Break
CALL SETMODE (fnum,15,,,old^value);! Obtains current values
CALL SETMODE (fnum,15,timeout,2);
CALL CONTROL (fnum,15); ! line in "space" condition.
! CONTROL completes immediately.
! error = 0.
CALL WRITE (fnum,....); ! output break disabled and WRITE
! active.
CALL SETMODE (fnum,15,old^value[0],old^value[1]);
! Restores values