AutomationDirect DL105, User Manual

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CPU
S
pecifications
and
Operation
4--17
CPU Specifications and Operation
DL105 PLC User Manual, 3rd Edition
There are a few things you can do the help improve throughput.
S
You can choose instructions with faster execution times
S
You can use immediate I/O instructions (which update the I/O points
during the program execution)
S
You can use the HSIO Mode 50 Pulse Catch features designed to
operate in high-speed environments. See the Chapter 3 for details on
using this feature.
Of these three things the Immediate I/O instructions are probably the most important
and most useful. The following example shows how an immediate input instruction
and immediate output instruction would affect the response time.
Solve
Program
Read
Input
Immediate
Normal
Write
Outputs
Solve
Program
Scan
Solve
Program
Field Input
Input
Off/On Delay
Output
Off/On Delay
I/O Response Time
Scan
Solve
Program
Normal
Read
Input
Write
Output
Immediate
In this case, you can calculate the response time by simply adding the following
items.
Input Delay + Instruction Execution Time + Output Delay = Response Time
The instruction execution time would be calculated by adding the time for the
immediate input instruction, the immediate output instruction, and any other
instructions in between the two.
NOTE: Even though the immediate instruction reads the most current status from
I/O, it only uses the results to solve that one instruction. It does not use the new
status to update the image register. Therefore, any regular instructions that follow
will still use the image register values. Any immediate instructions that follow will
access the I/O again to update the status.
Improving
Response Time