Rockwell Automation 1747-PCINT API Software for 1746 I/O - Manual (Page 124)

6–70 Library of Routines OC_SetOutputUpdate Mode
Publication 1747-6.5.3 June 1998
OC_SetOutputUpdate
Mode OC_SetOutputUpdateMode controls how the scanner updates real outputs from the
Output Image.
Syntax:
int OC_SetOutputUpdateMode(HANDLE handle, int mode);
Parameters:
Description:
This function does not affect input image scanning.
Setting the output update mode to OUTUPD_NEVER allows the host application to read the input image
and perform logic to determine the initial state of outputs. Once the output image is written with the initial
state data, the output update mode can be changed to allow updating of the outputs.
Setting the output update mode to OUTUPD_CHANGE allows the host application to signal the scanner
to write outputs by calling OC_WriteOutputImage. This setting allows the scanner’s minimum scan time
to be reduced (since it is only scanning inputs most of the time), and is provided as a performance
enhancement.
Setting the output update mode to OUTUPD_ALWAYS forces the scanner to write outputs from the output
image on every scan.
Parameter: Description:
handle Must be a valid handle returned from OC_OpenScanner
mode
If mode is:
OUTUPD_NEVER the scanner does not write outputs from the output
image unless explicitly requested by the
OC_DemandOutputScan function
OUTUPD_CHANGE the scanner writes outputs only when the scanner
output image is written via OC_WriteOutputImage,
but does not continuously update outputs from the
output image every scan
OUTUPD_ALWAYS the scanner continuously updates outputs from the
output image on every scan.
By default, the output update mode is OUTUPD_NEVER. A change in status
of the output update mode will take effect at the start of the next scan.