VIPA CP 1413plus, Руководство пользователя

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H1 Layer 4 program interface CP1413plus manual
4-38 Rev. 00/07
4.2.3.10 Check read
#include <H1Def.h>
unsigned short WENTRY_C H1CheckRead(H1_RECPARAMS W_POINTER rec)
This function determines whether a read task that was initiated by means of
H1StartRead
is still
active.
Parameters
rec
Pointer to a structure containing receive parameters. Parameters Vnr
and DataLen must contain the respective values. Ensure that the
buffer at the end of the structure is large enough.
Possible values returned by
rec.Fehler
:
0
H1_WAIT_CONNECT
H1_BLOCKED_DATA
H1_BAD_LINE
H1_WAIT_DATA
H1_NO_DRIVER
H1_NO_ADAPTER
H1_NO_REQUEST
Return value
< >
0
The operating system has detected an error.
0
The
rec.Fehler
element contains one of the values mentioned
above.
Note
This function is normally executed in singletasking systems. You may not mix the
H1ReadData
and
H1StartRead
/
H1CheckRead
tasks for a single
connection. The driver must first be initiated by means of
H1DriverOpen
and a
connection must also be established by executing
H1StartConnect
or
H1StartConnectCard
. When a value of
H1_WAIT_SEND
is returned the
H1CheckRead
function must be repeated (polling).
See also
H1DriverOpen
H1DriverClose
H1StartConnect
H1StartConnectCard
H1ReadData
H1StartRead
The following page contains a flowchart that shows how you should use these functions in your
programs.
The example for a read operation shown in chapter 6 operates according to this flowchart.