Omron SYSMAC CP Series User Manual

3 CPU Unit Operation
3-2
CP2E CPU Unit Software User’s Manual(W614)
3-1 CPU Unit Operation
This section gives an overview of the CPU Unit operation, describes the operating modes, and explains
how the Unit operates when there is a power interruption.
The CPU Unit reads and writes data to the internal I/O memory areas while executing user ladder pro-
grams by executing the instructions in order one at a time from the start to the end.
Self-diagnosis, such as an I/O bus check, is performed.
Instructions are executed from the beginning of the program and I/O memory is refreshed.
Data to and from external devices, such as sensors and switches, directly connected to the built-in I/O
terminals and expansion I/O terminals, is exchanged with data in the I/O memory of the PLC. This pro-
cess of data exchange is called the I/O refresh.
Peripheral servicing is used to communicate with devices connected to the communications port or for
exchanging data with the CX-Programmer.
The cycle time is the time between one I/O refresh and the next.
3-1-1 Overview of CPU Unit Operation
Overhead Processing (Self-diagnosis)
Ladder Program Execution
I/O Refresh
Peripheral Servicing
Cycle Time
00111010
11011000
10101001
00000000
00000000
10111011
11001010
10001101
01010100
01101010
CPU Unit Internal Memory
CPU Unit
processing
cycle
Overhead processing
(self-diagnosis)
Program execution
I/O refreshing
Peripheral servicing
Access
I/O memory
Change in status
after all instructions
have been executed
Exchange
Refreshes external devices at this timing
Inputs
Outputs

Omron SYSMAC CP Series Specifications

General

Brand	Omron
Model	SYSMAC CP Series
Category	Computer Hardware
Language	English