Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 91)

Chapter
8
8-1
Block Transfer
This chapter explains how to transfer data between intelligent I/O modules
(block transfer modules) and your program’s data area. After reading this
chapter you should be able to:
read a block of data from an intelligent I/O module
write a block of data to an intelligent I/O module
calculate how long it takes any given block transfer to finish
poll for completion of the block transfer
use a library routine to display the results on screen or printer or format
them to a file.
perform block transfers to a PLC5 in adapter mode
perform block transfers to a 1771–DCM.
To make this chapter shorter and easier to read, we use the abbreviation BT
for block transfer.
Here is a summary of the actions involved in completing a BT:
Your program puts the BT length into a packet of specified structure.
For a write BT, your program also puts the data into the packet.
Your program calls bt_que or another library routine.
The library routine adds your BT to its queue and interrupts the scanner
to alert it that the host has a request. The library routine writes a status
of “not complete” in your packet and returns control to your program
without waiting for a response from the scanner.
A short time later, the scanner responds to the interrupt and the host’s
interrupt handler puts the BT information into the global RAM.
Although this action interrupts your program, you can think of it as
something that takes place in background.
Chapter Objectives
Overview