How Omron plc works
Here, the basic actions common to the SYSMAC PLC of our PLC (programmable controller) are explained to the customers who have chosen the PLC for the first time. It does not include the technical information you need to purchase the FA system and plc programming.
I/O refresh
In the PLC (Programmable Controller), the user program designed by the customer performs the instruction from the beginning to the end by reading and writing the information in the memory area of ​​the PLC (Omron called "I/O memory"). deal with. On the other hand, data other than the PLC such as the Sensor/switch directly connected to the PLC or I/O unit is updated with the data of the "I/O memory" in the PLC at a certain timing. The data outside the PLC is updated together with the data of the I/O memory in the PLC, which is called "I/O refresh operation".
Understanding the timing of I/O refresh is very important when studying the actions of the FA system and user program designed by the customer. In the case of SYSMAC PLC, this I/O refresh operation will be performed immediately after all instructions have been executed. (see the figure below)
period time
In the PLC processing cycle, the time between the I/O refresh execution (start) and the next I/O refresh execution (processing), that is, the cycle time.
The cycle time includes the time required for common processing (self-diagnosis), user program execution processing, I/O refresh processing, peripheral service processing, and the like.
1 If the cycle time is too long, the cycle of data update with the PLC becomes longer, and the response time of the input and output becomes longer, resulting in failure to acquire changes in the input that are shorter than the cycle time.
2 If the cycle time is short, the response time of the input and output becomes shorter, and high-speed processing is possible.
3 If the cycle time is changed, the execution interval of the command and the response time of the input and output will also change.
In the case of SYSMAC PLC, the cycle time can be calculated by the following steps.
Cycle time = common processing time + instruction execution time + I / O refresh time + peripheral service time
The calculation method of the execution time of each SYSMAC PLC model is described in the product manual.
Interrupt task
Usually, during the processing cycle of the PLC, the user program includes other processing such as I/O refresh, which will be executed in order. (See the "I/O Refresh" item).
The processing that can be performed preferentially during this processing cycle is to interrupt the task. If the interrupt condition specified in advance is established, the processing cycle is interrupted and the processing is executed first.
(Depending on the SYSMAC PLC model, there is also a case where the "interrupt task" is expressed as "interrupt program". In this document, the "interrupt task" representation used in the CS/CJ series is explained).
For example, in the SYSMAC CS/CJ series, as an interrupt task, a power-off interrupt, a timer interrupt, an I/O interrupt, a constant-cycle interrupt by an internal timer, and an external interrupt can be provided.
Main interrupt task
content
Power interruption
Execute when power is cut off
Timed interrupt
Execute at regular intervals
I/O interrupt
Executed at the rising edge of the contact of the interrupt input unit
External Interrupt
There are high-function I/O units, CPU high-function units, and interposer boards.
Execute at request (CS series only)
I/O allocation
In the user program, in order to process the input and output signals of the I/O unit loaded in the PLC, it is necessary to assign the address of the I/O memory in the PLC to it in advance. The input and output signals of the units loaded in the PLC are allocated to the I/O memory, which is the I/O allocation. The CPU unit executes the loading unit and the I/O refresh operation based on the I/O allocation information.
How Omron plc works
The input and output signals of the units loaded in the PLC are allocated to the I/O memory, which is the I/O allocation. The CPU unit executes the loading unit and the I/O refresh operation based on the I/O allocation information.
Online automatic login
Offline automatic login
CPU unit storage area
In the PLC, processing of various types of data such as user programs, I/O memory data and comment information, setting information of the CPU unit and high-function unit, and registration I/O table information are performed. The place where all the data processed by these PLCs is stored, that is, the storage area in the CPU unit.
When SYSMAC PLC, there are three storage areas, which are supported by the battery.
In addition, in the SYSMAC CS/CJ series, the contents of the storage area can be supported by the built-in flash memory, and the data of the user program and the parameter area will not disappear even if the voltage of the battery is lowered.
User program area
Record the user program designed by the customer.
I/O memory area
This area can be accessed by the opcode of the instruction. Record channel I/O (CIO), internal auxiliary relay, hold relay, special auxiliary relay, data memory, extended data memory, timing completion flag, current value, count completion flag, current value, task flag, index register, data register Information such as condition registers, clock pulses, etc.
The data of the I/O memory area includes an area where the content is cleared when the power is restored, and an area where the previous information can be maintained.
Parameter area
Various initial setting information processed by the PLC.
Record information such as PLC system settings, login I/O tables, routing tables, and CPU high-function unit system settings.
Multi function remote manual pulse generator for control of all axes.
Manual Sensor,Miniature Optical Kit Encoder,Rotary Encoder With Led Ring,Optical Quadrature Encoder
Yuheng Optics Co., Ltd.(Changchun) , https://www.yhenoptics.com