Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 55)

Chapter 5
Startup, Status, and Shutdown
5-12
Why is shutdown required?
Your application program must shut down the scanner properly before
exiting back to DOS. There are two reasons to do this:
An orderly shutdown puts all output modules into last state or reset,
according to the switches set on the I/O chassis. This would happen
without an orderly shutdown, but would take about 100ms longer.
When your program issued the original call to setup_6008 or
start_6008, the driver routines altered the DOS interrupt vectors to
point to library routines linked in your executable file. The shutdown
routine resets those interrupt vectors. If your program exits without
resetting the interrupt vectors, and you then try to run a program that
overlays the area pointed to by the altered interrupt vectors, the host
computer may lock up or behave erratically, requiring a hard reset or
cycling power before you can use it again.
stop_6008
This function de-installs the scanner interrupt code. If a setup_6008 or
start_6008 function has once been executed successfully, your program
must call this function before exiting.
Calling sequence:
stop_6008( );
Arguments:
none.
Returned values:
none.
Your program can omit the stop_6008 call only if the initial setup_6008 or
start_6008 call failed. However, an extra stop_6008 call does no harm,
even where it’s not needed.
Shutdown