ReadBlock

(VTSDriver Library)

Description	Is launched to read a block of data from the PLC. It maintains a linked list of pointers to tag values with their absolute offset into the PLC file being read by this instance.
Warning	This function should be used only by advanced programmers. It is used only as a part of the VTSDriver module. Engineers writing a driver will not need to call this function directly.
Returns	Linked List
Usage	Script Only.
Function Groups	Stream and Socket
Related to:
Format:	…\Driver\ReadBlock(Info1, Info2, Info3, DType)
Parameters

Info1

Driver dependent. The first grouping parameter.

Info2

The second grouping parameter.

Info3

The third grouping parameter.

DType

The data type to read from the I/O device.

Comments

Launched from a script, runs in steady state. This module itself is in a global linked list of instances maintained by the VTSDriver module. This block represents all of the data to be read from a specific file in a specified PLC. All scan rates are handled by this one instance. This module keeps a list of nodes sorted by scan rates. These nodes point to another list of all the memory requests within that scan rate. This module will determine the best organization of blocks and launch a separate read module for each actual block of data read.