Rockwell Automation 1785-L20C_L40C, D17856.5.14 ControlNet PLC-5 Programmable Controllers User Manual - Manual (Page 62)

Chapter 4
Programming Your ControlNet System
4-7
For more detailed information on writing ladder programs, see the PLC-5
Programming Software Instruction Set Reference, publication 6200-6.4.11,
and PLC-5 Programming Software Programming, publication 6200-6.4.7.
For information on programming ControlNet I/O transfers using
Immediate Input (INN) and Immediate Output (IOT) instructions, see the
PLC-5 Programming Software Instruction Set Reference, publication
6200-6.4.11.
You must be careful when using Selectable Timed Interrupts (STIs)
with a program on a ControlNet network.
A Selectable Timed Interrupt (STI) periodically interrupts primary
program execution in order to run a subprogram to completion. If an STI
occurs while a normal ControlNet non-discrete I/O data transfer or a
ControlNet Immediate Data I/O instruction (IDO or IDI) is in progress and
they both operate on the same set of data, the integrity of that block of data
is jeopardized.
To ensure data-block integrity, write your STI routine so that it operates
on its own copy of the data block that it needs. Use ControlNet Immediate
Data I/O instructions (IDO and IDI) within your STI to copy the needed
block of data out to and back from a temporary location that is different
from that used by the normal data table.
For detailed information on STIs, see PLC-5 Programming Software
Configuration and Maintenance, publication 6200-6.4.6.
More
Using Selectable Timed
Interrupts with a Program
on a ControlNet Network
More