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How Block Transfer Works
Allen-Bradley Parts
Issuing Block transfer Commands
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
To make this chapter shorter and easier to read, we use the abbreviation BT
for block transfer.
Here is the sequence of actions involved in completing a BT:
Your program initializes the KTx command buffer with BT
command data.
Your program interrupts the KTx, letting it know it is a
command interrupt.
A short time later, the scanner responds to the interrupt and verifies that
the BT command is syntactically correct.
When the BT is complete, or if it is not finished within 4 seconds after it
was queued, the scanner interrupts the host with a confirmation. For a
read BT, if the BT was successful, the scanner also returns the data that
it read.
In the following sections we'll be taking a closer look at these steps.
Chapter
5
5-1
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