FAQ: How many cam table points are available in the MPiec Series Controllers?
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The number of cam table points available depends on several factors, including memory allocation set through the IEC environment, the number of active cam tables at any given time, and how cams are being used by the application.
The first factor is the memory allocation in the controller which only applies to the MP23xxiec. This determines how much memory is available for cam tables and how much is available for program execution. In the default memory configuration, the MP23xxiec controller has 7.5MB dedicated to active cam tables and 3.5 MB for the running memory of the IEC program. Large IEC programs, however, may require more running memory than the default, so there is an option in MotionWorks IEC to change from the default memory settings to 6.5 MB for the running memory and only 4.5MB of memory for active cam tables. This memory allocation function is not available with the MP2600iec controller because it is unlikely that a single-axis program will run into memory limits. It is also unnecessary with the MP3200iec controller because due to a much greater available memory (20MB for running cam tables and 52MB for IEC program memory).
Each point in a cam table (master/follower pair) consumes 16 bytes of memory. A typical cam table may have a 360 degree master cycle and a desired resolution of 0.1 degrees (a master/follower pair ever 0.1 degrees or 3600 pairs total). This would require only 57600 bytes (0.055 MB) of memory. Even at the minimum memory settings, over 300 cam tables of this size could be active. A higher resolution would obviously require more memory.
If application requirements require more cam table points than the available memory allows, there are a few options for reducing the cam table memory requirements:
-- Reduce the master axis resolution for the cam table (or part of it):
If the actual master position falls between two points on the cam table, the controller will automatically do a linear interpolation based on the previous and next master positions. Therefore, straight-line segments of the cam table, i.e. segments where the master and slave have a linear relationship, can be defined with only a start point and an end point.
-- Use the CamGenerator function block for on-the-fly cam table generation:
Often, flexible cam tables are required to allow for several different products or processes. However, a hundred different products doesn't have to mean 100 different cam tables are required. In most applications, only a few key parameters change from product to product. In these cases Yaskawa recommends calculating cam tables on-the-fly with the CamGenerator function block (found in the Cam Toolbox).
-- Use the Y_ReleaseCamTable function block to free up memory from cam tables no longer needed:
Cam tables will continue to take up memory even if they are no longer being used. To reclaim this memory, use the Y_ReleaseCamTable function block (found in the PLCopen_Plus firmware library).
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