csmstr - Omega Engineering

CONFIGURING DATA TAGS
EDITING FLAG TAGS
THE DATA TAB (VARIABLES)
The Data tab of a flag variable contains the following properties...
• The Mapping property is used to specify if the variable is to be mapped to a
register in a remote device, or if it exists only within the Master. If you press the
arrow button and select a device name from the resulting menu, you will be
presented with a dialog box that will allow a PLC register to be selected.
• The Bit Number property is used when a flag variable is mapped to a PLC
register which contains more than a single bit of information. The property is
then used to indicate which bit within the register is to be accessed by the tag.
• The Access property is used to specify what sort of data transfers should be
performed for a mapped variable. You may indicate that data is to be both read
and written, or just read or written as appropriate. Write-only tags can be used to
avoid unnecessary read operations on data that can only be changed by the
Master. They will typically be set to retentive as their value cannot be obtained
from the PLC, and must therefore be stored by the Master.
• The Storage property is used to indicate whether Crimson should allocate
FLASH memory within the Master in order to retain the value of the tag during
power-down. Mapped tags that are not write-only cannot be set to retentive, as
their values will in any case be read from the PLC, and it does not therefore
make sense to waste local storage to retain data that will be overwritten.
• The Simulation property is used to select the value that Crimson will assign to
this tag when displaying it within the display page editor. This facility can be
useful for documenting databases, in that it allows a display page to be
configured to represent a particular machine state, such that a screen capture can
then be pasted into an operator manual or other documentation.
• The Setpoint properties are used to indicate whether a setpoint will be specified
for this tag, and what that setpoint will be. Setpoints are used by certain alarm
modes, and allow the actual state of a tag to be compared to its intended state.
For example, a tag that represents the state of an input from a speed switch for a
REVISION 6 PAGE 109