Rockwell Automation 57C428 Toledo Scale Interface Module - Manual (Page 23)

4Ć7
Two Gross Weight calculations are made by the Interface software.
The `signed' Gross Weight is computed by first applying the `sign' bit
from Status Word `B' to the Indicated Weight and then adding the
Tare Weight. The result is stored as a double integer in registers 73,
74. The absolute value of the `signed' Gross Weight is stored in
registers 75, 76.
A comparison of the `signed' Gross Weight is made with each of the
eight Setpoints in registers 24Ć39. If the `signed' Gross Weight is less
than the Setpoint, the flag bit in register 77 is set to a 1 (TRUE);
otherwise, the bit is set to zero (FALSE). The comparison flag for
Setpoint #1 is in bit 0, Setpoint #2 in bit 1, etc.
4.2 Configuration
Before any application programs can be written, it in necessary to
configure, or set, the definitions of systemĆwide variables, i.e. those
that must be globally accessible to all tasks.
For DCS 5000 and AutoMax Version 2.1 and earlier, you define
systemĆwide variables by writing a Configuration task. For AutoMax
Version 3.0 and later, you define systemĆwide variables using the
AutoMax Programming Executive. After these variables are defined,
you can generate the configuration file automatically, which
eliminates the requirement to write a configuration task for the rack. If
you are using AutoMax version 2.1 or earlier, refer to Appendix E for
examples that show how to define variables in the configuration task.
If you are using AutoMax Version 3.0 or later, see the AutoMax
Programming Executive (JĆ3750) for information about configuring
variables.
4.3 Reading Data in Application Tasks
The frequency with which tasks read their inputs depends on the
language being used. Ladder logic and control block tasks read
inputs once at the beginning of each scan and write outputs once at
the end of each scan, regardless of how often the inputs are
referenced in the task. BASIC tasks read an input and write an output
for each reference throughout the scan.
In order for the interface module to be referenced by application
software it is necessary to assign symbolic names to the registers on
the module. In AutoMax Version 2.1 and earlier, this is accomplished
by IODEF statements in the configuration task. Refer to Appendix E
for a example. In AutoMax Version 3.0 and later,you can assign
symbolic names using the Programming Executive.
Each application task that references the symbolic names assigned
to the interface module must declare those names COMMON.