Types of m files, Transfer modes – Rockwell Automation GMLC Reference Manual User Manual
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Publication GMLC-5.2 - November 1999
794
1394 GMC Turbo SLC Interface
If an M file contains both integers and floating points, the floating point
elements are located in front of the integer elements. Use the formula
below to determine the proportions of your combination:
(number of floating points x 2) + (number of integers)
≤
512
For example: If your M file contains 100 floating-point elements, the
maximum number of integer elements available is 312.
M files can be accessed using indirect variables. This allows elements in
the M file to be indexed like an array. M file variables do not need
assigned names to be referenced indirectly.
Types of M Files
There are two types of M Files:
•
M1 files are used to transfer data from the 1394 GMC Turbo to the
SLC.
•
M0 files are used to transfer data from the SLC to the 1394 GMC
Turbo.
Transfer Modes
GML Commander supports two different M file update modes:
•
Automatic (auto) mode.
•
Handshaking (manual) mode.
Auto Mode
When auto mode is enabled, the SLC notifies the 1394 GMC Turbo every
time it writes new data to the M0 file. The 1394 GMC Turbo does not
know which portion of the M0 file has been updated, and therefore copies
the entire file each time—even if only one element was written.
Depending on your application and the size of your M files, these
numerous updates can impact your CPU utilization. Auto mode is ideal
for applications with small M files containing elements that do not have to
be updated simultaneously.