Omron CJ1G-CPU series, Programming Manual

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6
Internal Structure of the CPU Unit Section 1-3
1-3 Internal Structure of the CPU Unit
1-3-1 Overview
The following diagram shows the internal structure of the CPU Unit.
The User Program The user program is created from up to 288 program tasks, including interrupt
tasks. The tasks are transferred to the CPU Unit from the CX-Programmer
programming software.
There are two types of tasks. The first is a cyclic task that is executed once
per cycle (maximum of 32) and the other is an interrupt task that is executed
only when the interrupt conditions occur (maximum of 256). Cyclic tasks are
executed in numerical order.
Note With the CS1-H, CJ1-H, or CJ1M CPU Units, interrupt tasks can be executed
cyclically in the same way as cyclic tasks. These are called “extra cyclic
tasks.” The total number of tasks that can be executed cyclically must be 288
or less.
Program instructions read and write to I/O memory and are executed in order
starting at the top of the program. After all cyclic tasks are executed, the I/O
for all Units are refreshed, and the cycle repeats again starting at the lowest
cyclic task number.
Refer to the section on CPU Unit operation in the CS/CJ Series Operation
Manual for details on refreshing I/O.
I/O Memory I/O memory is the RAM area used for reading and writing from the user pro-
gram. It is comprised of one area that is cleared when power is turned ON and
OFF, and another area that will retain data.
I/O memory is also partitioned into an area that exchanges data with all Units
and an area strictly for internal use. Data is exchanged with all Units once per
program execution cycle and also when specific instructions are executed.
CPU Unit
Task 1
Task 2
Task n
The programm is divided
into tasks and the tasks
are executed in order by
task number.
Memory Card
I/O memory, PC Setup,
programs and the EM area
can be saved as files.
User program
I/O memory
EM file memory
PLC Setup
and other
parameters
DIP switch
Auto-
matic
backup
Flash
memory
Access
Auto-
matic
backup
(CS1-H, CJ1-H, or
CJ1M CPU Units only)