AC500/S500: Short Description Hardware

Processor Modules

AC500 Processor Modules contains the CPU with the core component of the PLC. The CPU is connected with the user memory, input and output module, communication port and other units via system bus and performs tasks by means of system programs preset in the system memory. The CPU adopts the function preset by the system program to command the PLC for operation.

Its functions include:

• To receive user program and data entered
• To diagnose work faults of the power supply and PLC circuit as well as syntax error in programming
• To receive the state or data of the site via the input interface and save it into the shadow register or data register
• To read the user program in the memory one by one and execute it after interpretation
• To update the state of related flag bits and output shadow register contents according to execution results and realize output control by means of output unit.

Processor Modules are available in different performance classes. Only one Processor Module is required for a valid system architecture.

There are different types of Processor Module available that differ in the features and functions they provide, e.g. performance, LED display etc.

If required, Processor Modules are also available with an integrated ETHERNET Communication Module (TCP/IP).

Communication Modules

AC500 communication modules are required for

• a connection to standard field bus systems and
• for integration into existing networks.

AC500 communication modules

• enable communication on different field buses.

• are mounted on the left side of the processor module on the same terminal base.

• are directly powered via the internal communication module bus of the terminal base.

  A separate voltage source is not required.

I/O Modules

The I/O Modules are the input / output unit which connects the PLC with the industrial production site. The PLC can detect controlled object data via the input interface and the data is taken as the basis for PLC control on the controlled object. In addition, the PLC sends processing results via the output interface to the controlled object to realize the control purpose.

External input equipment and output equipment need various signal levels while the information processed by the CPU in the PLC only can be the standard level. In order to realize such conversion, the I/O interface generally shall perform optical isolation and filtering to improve interference immunity of the PLC. In addition, the I/O interface generally can indicate the working state to facilitate maintenance.

The PLC provides multiple I/O interface for operation level and drive capability to users for selection such as digital input, digital output, analog input, analog output, etc. I/O interfaces of the PLC have the number of input / output signals taken as the number of PLC I/O points. The number of I/O points is an important basis for PLC selection. If the system is insufficient in the I/O points, it can be expanded via the I/O extension interface of the PLC.

The I/O Modules for digital and/or analog inputs and outputs are available in different versions and allow flexible use thanks to configurable channels.

The modules can be simply plugged onto a Terminal Unit for central expansion or decentralized expansion via Communication Interface Modules.

Function Modules

Function Modules extend the PLC system to perform special task control. Those modules often provide independent components such as a CPU, system programs, memory and interfaces connected with the PLC system bus.

It is connected with the PLC via the I/O bus to exchange data and independently work under cooperative management of the PLC.

Communication Interface Modules

Communication Interface Modules enable decentralized expansion by I/O Modules. It contains embedded digital I/Os and a fieldbus interface.

Communication Interface Modules act as I/O slave devices within a master-slave-arrangement.

The remote I/O system also must be equipped with corresponding communication interface modules.

Terminal Bases

On a Terminal Base the Processor Module and the Communication Modules are plugged.

Note

For AC500-eCo Processor Modules and special AC500 (Standard) Processor Modules the Terminal Base cannot be removed.

Terminal Units

On a Terminal Unit the I/O Modules are plugged.

Terminal Units enable simple prewiring without electronics and are available for 24 VDC and 230 VAC, optionally for spring or screw-type terminals.

Memory

In the PLC, the memory is mainly used for saving system programs, user programs and work data. The following memory types can be distinguished:

• Volatile memory:

  All saved data will be lost after power failure of the memory but the memory can provide high access rate and unlimited programming cycles. Common volatile memories mainly include SRAM and DRAM (including common memories such as SDRAM).

• Nonvolatile memory:

  All saved data will not be lost after power failure of the memory, but the memory is subject to low read-write rate and limited rewrite cycles. Common nonvolatile memories mainly include NORflash, NANDflash, EEPROM, SD card, etc.

AC500 PLCs store all user programs in the nonvolatile memory to get protected from power failure. The programs are exported to the volatile memory under operation of the PLC to ensure high-speed and efficient operation. If user program debugging is finished, the programs can be fixed in the nonvolatile memory when they need no change. The work data is subject to frequent change and access in the PLC operation. It is saved in the volatile memory to meet the requirements for random access.

The work data memory of PLC has the memory area for input and output relay, auxiliary relay, timer, counter and other logic devices. The state of these devices depends on initial setting and operation of the user programs. Some data maintains existing state by using built-in supercapacitors or backup batteries in case of power failure. The memory area for data saving in case of power failure is called the data retention area.

Power Supply

The PLC is equipped with a switch power supply for internal circuit. Compared with ordinary power supply, the PLC power supply has the higher stability and interference immunity. A number of PLC products provide DC 24 V stabilized voltage supply to meet external sensors.