Cpu Unit Internal Operation; Overview; Startup Initialization - Omron CJ2 - 02-2010 User Manual

3 CPU Unit Operation
3-1

CPU Unit Internal Operation

3-1-1

Overview

The CPU Unit writes data to the internal I/O memory areas while it cyclically executes user programs.
Data is exchanged externally when I/O is refreshed and peripherals are serviced. The following figure
shows the internal operation of the CPU Unit.

Startup initialization

(1) Overseeing processing
(2) Program execution
(3) Peripheral servicing
(4) I/O refreshing
Startup Initialization
The following processes will be performed once each time the power is turned ON to the PLC.
• Detecting connected Units (I/O allocation)
• Comparing the registered I/O tables and the connected Units
• Clearing the non-holding areas in I/O memory according to the status of the IOM Hold Bit
• Clearing forced status according to the status of the Forced Status Hold Bit
• Autobooting using the autotransfer files in the Memory Card if one is inserted
• Performing self-diagnosis (user memory check)
• Restoring the user program
• Updating the PLC Setup
3-2
Pro-
cessing
cycle
Configuration
Units
Cycle
time
CJ2 CPU Unit Software User's Manual