(VTSDriver Library)
Description: This module 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 is for use by advanced programmers only. This function is used only as a part of the VTSDriver module.
Returns: Linked List
Usage: Script
Format: …\Driver\ReadBlock(Info1, Info2, Info3, DType)
Parameters: Info1 is the first grouping parameter.
Info2 is the first grouping parameter.
Info3 is the first grouping parameter.
DType is 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.