Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 27)

4Ć7
considered outputs: command registers, application registers,
the ISCR (interrupt status and control register), scans per
interrupt register, and scans per interrupt counter register. See
the AutoMax Programming Executive for more information on
the STOP ALL and system reĆinitialization conditions.
2. Common
Common variables are variables that are defined in the rack
configuration and are therefore accessible to all application
tasks in the rack. There are two types of common variables,
those that refer to memory locations, and those that refer to
actual physical I/O locations. The two types are defined
differently in the configuration for the rack.
Common memory variables can be of any data type. They may
be read to or written from. Common I/O variables are long
integer, integer, or boolean variables that represent actual
physical I/O locations. Common I/O variables that represent
inputs may be read but not written to. I/O variables that
represent outputs may be read or written to.
All BASIC and Control Block tasks that need to access common
variables can do so by using the BASIC statement COMMON (or
GLOBAL). For Ladder Logic/PC tasks, the editor prompts for
whether the variable is local or common when the task is being
created. At least one task in the rack should also initialize
common memory variables, i.e., assign values to them, if they
need to be at a known state other than 0.
The value of common variables at the time of initial task
installation depends upon whether the variable references
memory or physical I/O locations. Common memory variables
are always 0 at task installation. Common I/O variables that
represent outputs are always 0. Common I/O variables that
represent inputs are always at their actual state.
After a STOP ALL condition or a power failure followed by a
systemĆrestart, common memory variables that are defined as
volatile memory statements in the configuration are 0. Common
memory variables that are defined as nonĆvolatile memory in the
configuration retain their last value. Common variables that
represent I/O locations are at 0 for outputs and at their actual
state for inputs. Note that the UDC dual port memory is treated
like I/O variables. See the AutoMax Programming Executive for
more information on the STOP ALL and systemĆrestart
conditions.