Comtrol API (6508) for the MS-DOS - Manual (Page 34)

34 API Functions
EvModemChange
EvModemChange
Application modem input change event function
EvModemChange(Dev,unsigned char
MdmChange,unsigned char
MdmState)
int Dev Device number
unsigned char MdmChange Modem input lines which
changed. Can be any
combination of the
flags:
COM_MDM_DSR ,
COM_MDM_CTS , or
COM_MDM_CD .
If a flag is set that modem
line is changed, if a flag is
not set that modem line did
not change.
unsigned char MdmState Current state of the modem
inputs. Can be any
combination of the
COM_MDM_CTS ,
COM_MDM_DSR , and
COM_MDM_CD flags. If a
flag is set that modem line
is
ON , if a flag is not set
that modem line is OFF .
void
This function is not part of the API , it must be written
by the developer as part of the application program.
The function name EvModemChange is an example
name only, this event function can be given any name
desired.
This function is not called directly by the application.
Instead, it is dispatched by the
API ’s internal ISR
(interrupt service routine) when it detects that receive
data is available. Before this function will be
dispatched it must be installed with
aaInstallMdmChgEvent(), and modem input change
detection must be enabled. Detection is enabled using
the DetectEn parameter of aaOpen() or aaReconfigure().
The function installed here is called during an
interrupt service routine (
ISR ). Keep your code short
and remember that many standard C library calls do
Function
Purpose
Call
Return
Comments
Warning
not work in ISR s, such as printf().
If using the Microsoft C compiler, stack checking must
be disabled during the event function and any functions
called by the event function.
Stack checking can be turned off and on with:
#pragma check_stack(off)
#pragma check_stack(on)