Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 260)

Publication 1785-UM012D-EN-P - July 2005
17-2 Using Selectable Timed Interrupts
Online editing affects the performance of an STI routine. The STI cannot
interrupt the controller while it is managing its memory due to the online edits
being made. The STI input must be on for an amount of time slightly greater
than the actual time required to complete the online edits. If not, the STI does
not execute.
STI Application Example
Periodically check the status of PLC-5 family controllers on the DH+
communication link. Compare the status of each controller with a file of
reference data (see rungs below). Set a bit if a mismatch is found. Perform
this comparison once every 800 ms. Assume that another active step retrieves
status data from the PLC-5 controllers with a MSG instruction and loads it
into a temporary source file (N5:10).
Block-Transfers in Selectable Timed Interrupts (STIs)
If the controller runs an STI that contains block-transfer instructions, the
controller performs these block-transfers immediately on completing any
block-transfers currently in the active buffer, ahead of block-transfer requests
waiting in the queue.
You can program “immediate” block-transfers to a local I/O chassis using the
STI program (i.e., the STI is invoked and the block-transfer occurs
immediately). The controller executes the block-transfer immediately,
completes the remaining rungs in the STI, then resumes execution of the
ladder program.
Set the .TO bit on any block-transfer instruction destined for the same slot as
the block-transfer in the STI. These block-transfers only try to execute once so
as not to keep the STI from completing.
EN
FSC
FILE SEARCH/COMPARE
Control
Length
Position
Mode
R6:0
10
0
ALL
DN
R6:0
FD
O:000
00
ER
Expression
#N5:0 <> #N5:10
R6:0
DN
/