Technical Guide for PLC Basic CSM PLC Basic TG E 1 1 Introduction This guide will describe the terminology needed for basic operation of the SYSMAC PLC (Programmable Controller), for clients new to our PLCs. This guide does not cover technical details regarding the setting of the FA System or PLC programming after purchase. I/O Refresh With the PLC (Programmable Controller), commands from user programs designed by the client are executed one by one and processed by reading and writing information in the internal PLC memory area (At OMRON, we call this theI/O Memor). At the same time, packages of data from sensors/switches that are directly connected to the basic I/O unit are exchanged with data in the PLC internal I/O Memory, at specific times. This process to totally exchange external data and internal I/O memory data is calledI/O Refresh Operatio. It is important to know the timing by which the I/O Refresh will be executed when considering the operation of the FA System and User Programs designed by the client. In the case of the SYSMAC PLC, this I/O Refresh operation is performed immediately following the execution of all other commands. (See Figure below) PLC Inside PLC (CPU Unit) Common Processing (Self-Diagnosis) Basic I/O Unit or built-in I/O Change (after all I/O Memory commands executed) Package Execute Program 00000000 01010100 Read/Write Exchange 00000000 01101010 11011000 11001010 PLC 00111010 10111011 Processing Cycle 10101001 10001101 I/O Refresh Refresh with external devices Peripheral Servicing External Data (Sensor, Switch, Actuator etc.) Cycle Time In terms of the PLC processing cycle, the cycle time is the time from the execution (commencement) of the I/O Refresh operation to the execution (processing) of the following I/O Refresh. The cycle time includes time for overhead processing (self-diagnosis), execution of user programs, I/O Refresh processing and the processing of peripheral services. When the cycle time is long, the cycle for updating data from outside of the PLC and the I/O response time are also longer, making it impossible to implement changes that are input at a rate faster than the cycle time. When the cycle time is short, I/O response time is also shortened, which allows high speed processing. As the cycle time changes, the command executi on cycle and I/O response times also change. In the case of the SYSMAC PLC, the cycle time can be requested in the following manner: Cycle Time = Overhead Processing Time + Total Command Execution Time + I/O Refresh Time + Peripheral Service Time The calculation methods for each execution time for the SYSMAC PLC are included in the product manual. 1Interrupt Tasks Normally, user programs are executed in order along with the processing of the I/O Refresh etc., within the PLC processing cycle (See I/O Refres). Interrupt Tasks however are executed in precedence to this processing cycle. In the event that certain interrupt conditions are met, the processing cycle will be suspended and the interrupt tasks will be executed first. (The SYSMAC PLC sometimes refers to theInterrupt Task asInterrupt Program, but here we shall useInterrupt Task, the terminology used in the CS/CJ Series manuals) For example, in the case of the CS/CJ Series, Interrupt Tasks can include power Off interrupt, Scheduled Interrupts, I/O Interrupts, Periodic Interrupts based on the internal timer, and External Interrupts. Major Interrupt Tasks Details Power Break Interrupt Tasks Executed during a power break. Scheduled Interrupt Tasks Executed based on a specific schedule. I/O Interrupt Tasks Executed at the start-up of a connected Interrupt Input Unit. Executed when requests are received from the Special I/O unit, the CPU Bus Unit, and the INNER Board (only for CS External Interrupt Tasks Series). I/O Allocation In order for user programs to utilize I/O signals from the I/O Units mounted to the PLC, it is necessary to first assign an address within the PLC I/ O Memory. The assignment of I/O Memory to the input or output from these units within the PLC is known as I/O Allocation. The CPU Unit uses this I/O Allocation information in the operation of I/O Refresh with connected units. In the case of SYSMAC PLC, this I/O Allocation information is recorded in the PLC in theRegistered I/O Tabl. ThisRegistered I/O Tabl can be created by either automatically registering online with programming tools utilizing information from the unit built-in to the PLC, or by using programming tools to design offline and then automatically registering by transmitting the I/O table to the PLC. (Some devices may not require the creation of a Registered I/O Table, and others may not support the offline design of I/O Tables.) Online Automatic Registration CX-Programmer or Registered I/O Table Type and Location Programming Console of Mounted UnitsCreate I/O Tabl Operation CPU Unit I/O Units SYSMAC CJ/CS Series Offline Automatic Registration Type and locations of Edit Registered I/O Table the Mounted Units CX-ProgrammerCreate I/O Tabl Operation CPU Unit I/O Units SYSMAC CJ/CS Series 2