Bradley Smoker PLC-5 user manual Effects of Housekeeping Time, Editing While in Remote Run Mode

C-4Maximizing System Performance

Because the first program scan takes 28 ms, the STI actually occurs 12 ms into the second program scan (28 + 12 = 40, which is the time for the second STI to occur). This example points out that when the STI time period is different than the program scan time, the STI occurs in different places in the program scan. Also note that, due to fluctuations in program-scan times, multiple STIs may be executed during one scan and no STIs during other scans.

Effects of Housekeeping Time

In PLC-5 controllers, basic housekeeping takes 3.5 ms. If it takes the controller 21.8 ms to execute a ladder program, the overall program scan time is 25.3 ms. Any increase in housekeeping affects your program scan.

The following activities can increase housekeeping time:

•editing while in remote run mode

•putting block-transfer modules in the controller-resident chassis

•using the global status flag files

Editing While in Remote Run Mode

The online editing times for ladder programs are as follows:

For this Editing Operation	And this Type of	The Times are
	Program
Accept Rung (after inserting, modifying,	other than the edited file	0.35 ms per 1000 words
or deleting a rung edit)
	no labels	3 ms + 0.35 ms per 1000 words
	with labels	3.5 ms + 0.35 ms per 1000 words
Test Edits of the program (impacts one		0.2 ms to change the status of
program scan)		edits from TEST to UNTEST or
		UNTEST to TEST
Assemble Edits	no edits pending	0.35 ms per 1000 words
	edits pending, no labels	2.0 ms + 1.5 ms per 1000 words
	edits pending, with labels	2.0 ms + 1.9 ms per 1000 words

IMPORTANT

Editing programs online also delays the execution of PIIs and STIs.

Publication 1785-UM012D-EN-P - July 2005