B&B Electronics VFG3000 - Manual - Manual (Page 74)

E DITING F LAG T AGS V LINX F IELDBUS G ATEWAY M ANAGER U SER M ANUAL
P AGE 58
• The Simulation property is as described for flag variables. Note that the value to
be simulated applies to all elements of the array. If you need to simulate on a per
element basis, use a number of formulae to alias the array elements.
• The Read Policy property is used to define how Fieldbus Gateway Manager will
read the data for arrays that are mapped to remote data items. The table below
lists the various policies that can be configured, and describes their operation…
M
ODE
D
ESCRIPTION
Read Adaptively Any referenced array elements will be added to the
communications scan. Data either side of a referenced
element, as defined by the Read Ahead and Read Behind
properties, will be read as well. Old data may be
displayed momentarily when an element from an adaptive
array is first displayed on the Gateway.
Read Manually The array will be read if and only if the ReadData
function is called. This mode is useful for items that are
read only rarely, or which are known not to change in the
remote device.
Read Whole Array The entire array will be added to the communications
scan if any element in the array is referenced. This mode
ensures that all data items are available before they are
referenced, but can lower system performance.
• The Read Ahead and Read Behind properties modify the behavior of the adaptive
read policy by controlling how many adjoining registers will be read when a
specific array element is referenced. The adjoining reads are used to maximize
the chance of data being available when indirection is used to scroll up or down
an array. The default values should be suitable for most applications.
• The On Write property is as described for flag variables.
T
HE
F
ORMAT
T
AB
The Format tab of a flag tag contains the following properties...