CP82C55A

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The CP82C55A is a microcomputer peripheral circuit designed to provide microcomputers with additional input/output (I/O) lines. It is an I/O expander that enhances the microcomputer’s I/O capability and expands the number of peripherals.

The CP82C55A itself consists of 64 input/output lines that are organized into eight 8-bit ports (port 0 – port 7). Furthermore, it contains a dedicated address decoder that allow selection of any 1 of the 8 ports. The selection of ports can be done via electrical signals sent from the processor or microcontroller to the CP82C55A.

Application Field of CP82C55A

CP82C55A is widely used in the industrial control, numerical control and other control fields for adopting special functions. For example, in the industrial control fields, CP82C55A can be used to control the camera in industrial image processing, the electric gates in warehouse management, and so on. In the numerical control fields, CP82C55A can be used to control the stepper motors, servo motors, and spindle motors. Other than that, CP82C55A can also be used in various embedded control and display projects or even as a major part in microcontrollers.

Working Principle of CP82C55A

In the CP82C55A, the 64 I/Os are organized into 8 ports, which are port 0 to port 7. Port 0 and port 1 are 8-bit parallel input ports that are used to handle external inputs. Port 2 and port 3, on the other hand, are 8-bit parallel output ports that are used to provide signals to drive external parts such as indicator lamps, LED displays and LED indicators. The ports 4, 5 and 6 also have 8-bit directions, meaning these ports can be either used as input or output ports. Finally, port 7 has two 4-bit output ports and two 4-bit input ports.

The data on the 8-bit bus can be directly accessed and its states can be changed. The address decoder found in the CP82C55A plays the role of directing the data to the respective ports. When a specific address is requested by the microcontroller, the CP82C55A will determine which port is associated with the address, and will then execute the request accordingly. So, if the data is written to a certain address, the CP82C55A will send the data to the port associated with such address, while if it is requested to read a certain address, the CP82C55A will read the data from the port associated with such address.

Furthermore, the CP82C55A can also be setup to function in various modes. In the single-byte mode, only one byte of data is accessed at a time. In the multiple-byte mode, multiple bytes of data can be accessed at a time. And finally, in the autostart mode, the CP82C55A can start operations with a single instruction, so that it can run in a “background” state and execute instructions without involving the processor.

All in all, the CP82C55A is a handy I/O extension device that offers great flexibility in terms of its features, functions and working modes. By adding the I/O extension board, the microprocessor can be easily expanded thereby giving machine designers even more flexibility in choosing the best hardware solution for their needs.

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