Bradley Smoker PLC-5 user manual Using Global Status Flag Files, Calculating Throughput

Maximizing System Performance C-5

Putting Block-Transfer Modules in Controller-Resident Chassis

Because controller-resident racks cannot be updated until after active block-transfers are completed, putting block-transfer modules in the controller-resident chassis can affect housekeeping by a worst-case time of approximately 100 ∝s per one word of block-transfer data. Note that this estimate is based on a worst-case scenario. Typically, the effect, if any, on housekeeping will be minimal.

Using Global Status Flag Files

The global status flag files are updated during housekeeping. This increases housekeeping time as follows:

•each global status flag file on a channel (for example, channel 1A or 1B) adds 3ms

•housekeeping time does not increase more than 6ms, even if there are more than two global status flag files

If you need two global status flag files, split them across two channels.

Calculating Throughput

Throughput is the time that it takes for an output to be energized after its associated input has been energized. You need to consider the following components when evaluating throughput:

•input and output module delay

•I/O backplane transfer

•remote I/O scan time

•controller time

To calculate throughput, use the following equation:

Input				Worst-Case		Worst-Case		Worst-Case			Output
Card	+	I/O Backplane	+		+		+		+	I/O Backplane	+ Card
				Remote I/O		Processor		Remote I/O
Delay											Delay
				Scan Time		Time		Scan Time

Publication 1785-UM012D-EN-P - July 2005