Rockwell Automation 57C620 AutoMax Programming Executive Version 3.8 - Manual (Page 242)

DĆ2 AutoMax Programming Executive Version 3.x
Application Task Memory Utilization in the Rack
See section 10.0 for the amount of memory available on each Processor module.
In racks with a single Processor, add the total size of all the application tasks and
the configuration to determine the amount of memory they will require on the
Processor. In racks with multiple Processors, the configuration file will reside on
the Common Memory module (M/N 57C413 or M/N 57C423 in slot 0). To
determine the amount of memory that will be utilized on each Processor, add the
total size of all the application tasks that will reside on each Processor.
In rare cases, PC/Ladder Logic tasks that are within the limit specified above may
not be loadable on a Processor. This is due to the manner in which Processor
memory is allocated for bit variables in PC tasks. The smallest amount of
Processor memory that can be allocated for any PC task variable is one word (16
bits). Each 16Ćbit register used in the PC task requires one word of memory.
Individual bits within registers also require one word of memory. However, if more
than one bit in a register is used, all those bits can be stored in one word of
memory.
When there is a Common Memory module located in slot 0 of the rack (i.e., being
used for bus arbitration and common memory storage) there are approximately
1400 words (2.8K) of memory available on each Processor for storing PC task bit
variables. If there is no Common Memory module in the rack, or the Common
Memory module is in a slot other than 0 (i.e., serving as extra memory), there are
approximately 1000 (2K) words of memory available on each Processor for
storing PC task bit variables. The M/N 57C435 Processor has approximately 2000
words (4K) of memory available for storing PC task bit variables regardless of
whether or not a Common Memory module is in the rack.
This method of allocating space for bit variables will not cause a problem unless
you use a large number of single bits within different words. Note that if you have
run out of room for PC tasks for this reason, you can still load BASIC and Control
Block tasks up to the limit of the Processor's memory.
Note that each physical online connection (maximum of four, one to each
Processor) made through the Executive software either over the network or
directly to the rack will require an additional 5K of memory on the Common
Memory module. If there is no Common memory module, the 5K required will be
allocated from the Processor.