Comtrol API (6508) for the MS-DOS - Manual (Page 15)

Developing Applications 15
Developing Applications
2.8.2.7. Detection Enable Parameter
The detection enable parameter is used by aaOpen() and aaReconfigure() to set
which events are detected by the
API .
If a detection enable flag is set, an event function within the application is
dispatched when that event is detected. This assumes that the application has
installed the event function. See Subsection 2.12 for information about event
functions.
You can assign any combination of the flags shown in
Table 2-10 to the detection enable parameter. The detection enable parameter
is declared as follows:
unsigned int DetectEn;
2.8.2.8. Modem Control Parameter
The modem control parameter is used by aaOpen() to determine the initial
state of the modem control outputs. If a flag is set, the modem control line is
turned
ON ; otherwise it is OFF .
It is also used by aaClose() to determine which modem control outputs must be
cleared. If a flag is set, that modem control line is turned
OFF ; otherwise it is
not changed.
The modem control output flags are given in Table 2-11. The modem control
parameter is declared as follows:
unsigned ModemCtl;
2.9. Writing Serial Data
After a device is open, serial data can be written to it using aaWrite(). The
number of data bytes from previous aaWrite() calls that are still awaiting
transmission can be obtained with aaGetTxCount().
2.10. Exiting the Application
You must call aaExit() before exiting an application. This does final cleanup,
including removing the interrupt service routine (
ISR ) used by the API .
2.11. Reading Serial Data
After a device is open serial data can be read from it using aaRead(). The
number of receive data bytes that are buffered by the device can be obtained
with aaGetRxCount().
Using aaRead() by itself does not return any receive error information. If error
information is needed, you can determine if there are any errors in the device’s
receive buffer by calling aaGetRxStatus(). If errors exist, you can obtain the
error status of each receive data byte by reading the data with
aaReadWithStatus().
2.12. Installing and Detecting Events
When the controller needs to notify the system that something important has
occurred, it generates an interrupt and causes an event function to execute on
the system.
Event functions tell you what has happened and provide the appropriate
information for that event, which you can then process as needed.
The following receive events can occur on the system:
•
Modem change event, one of the modem lines has changed for a serial
device.
• Receive data event, data has been received on a serial device.
• Periodic event, occurs 274 times per second.
You need a way to tie your application to these events. This is accomplished by
calling the aaInstallxxxEvent functions. By using an aaInstallxxxEvent function,
COM_FLOW_OS Enable output software flow control
COM_FLOW_OH Enable output hardware flow control
using
CTS
COM_FLOW_OXANY Enable restart output on any Rx
character
Table 2-10. Detection Enable Flags
Flag Meaning When Flag Set
COM_DEN_NONE No event detection enabled
COM_DEN_MDM Enable modem control
change detection
COM_DEN_RDA Enable receive data available
detection
Table 2-9. Flow Control Flags (Continued)
Flag Meaning When Flag Set
Table 2-11. Modem Control Output Flags
Flag Modem Control Line
COM_MDM_RTS Request to send
COM_MDM_DTR Data terminal ready