ProSoft Technology MVI69-ADM - Manual (Page 210)

Backplane API Functions MVI-ADM ♦ 'C' Programmable
Developer's Guide 'C' Programmable Application Development Module
Page 210 of 342 ProSoft Technology, Inc.
February 20, 2013
8.3 Backplane API Synchronization Functions
MVIbp_WaitForInputScan
Syntax
int MVIbp_WaitForInputScan(MVIHANDLE handle, WORD timeout);
Parameters
handle Handle returned by previous call to MVIbp_Open
timeout Maximum number of milliseconds to wait for scan
Description
MVIbp_WaitForInputScan allows an application to synchronize with the scan of
the module’s input image. This function will return immediately after the input
image has been read. This function may also be used by a module application to
determine if the Flex I/O bus is active.
handle must be a valid handle returned from MVIbp_Open.
timeout specifies the number of milliseconds that the function will wait for the
input scan to occur.
Notes: There is no distinction in the MVI94 module between input and output scans. Therefore, the
MVIbp_WaitForInputScan and MVIbp_WaitForOutputScan functions will perform exactly the same
function and are interchangeable.
The scan time of the Flex I/O bus varies according to the number of modules installed. If the MVI-
ADM module is the only module present, then it will be scanned approximately every 200
microseconds. The maximum scan time for a full rack of 8 modules is approximately 1.6
milliseconds. Note that the scan time referred to here is not the PLC scan time, but the Flex I/O bus
scan time. The PLC scan time will depend upon which Flex adapter is used and how it is
configured.
MVI56 Note: This function is not supported for the MVI56 and will return
MVI_ERR_NOTSUPPORTED.
MVI94 Note: There is no distinction in the MVI94 module between input and output scans.
Therefore, the MVIbp_WaitForInputScan and MVIbp_WaitForOutputScan functions will perform
exactly the same function and are interchangeable.
Return Value
MVI_SUCCESS The input scan has occurred.
MVI_ERR_NOACCESS handle does not have access
MVI_ERR_TIMEOUT The timeout expired before an input scan occurred.
Example
MVIHANDLE Handle;
/* Wait here until input scan, 50ms timeout */
rc = MVIbp_WaitForInputScan(Handle, 50);
if (rc == MVI_ERR_TIMEOUT)
printf("Input scan did not occur within 50 milliseconds\n");
else