Rockwell Automation GMLC Reference Manual - Manual (Page 832)

Publication GMLC-5.2 - November 1999
Understanding M Files 795
Manual Mode
When manual mode is enabled, the 1394 GMC Turbo ignores the
automatic SLC update notifications and waits for the program to set a
system bit. This decreases the number of updates, and therefore
minimizes the impact on your CPU utilization. Manual mode is ideal for
applications with large M files containing elements that need to be
updated simultaneously.
For example: If your application requires position, velocity and
acceleration data to make a move, and those elements are located in a
file with 100 other elements, you must update all of the elements at
the same to make sure that the data you need is current.
Using auto mode, you cannot verify that the three elements you need
were updated at the same time because they may have been updated
at different points during the program.
Using manual mode, you can update all of the elements you need and
then transfer them all at the same time instead of updating each
element one at a time.
Updating M0 Files Using Manual Mode
When M0 files are updated using manual mode:
• The SLC program updates the M0 file variables and issues the M0
Update Request bit (bit 6).
• The GML Commander program sees the system bit variable
SLC_M0_Update_Request (bit 6) and sets the system bit variable
SLC_M0_Update_Acknowledge.
• The 1394 GMC Turbo system software waits for the GML
Commander program to set this bit and then starts the update.
• The SLC program waits for the M0 Update Acknowledge bit to be set
and then resets the M0 Update Request bit. This serves as a signal to
the 1394 GMC Turbo system that the SLC has recognized the start of
the update.