The UPD8155C is a programmable peripheral interface (PPI) chip manufactured by NEC. It's designed to work alongside microprocessors, particularly those in the Intel 8080/8085 family, to expand their input/output capabilities and provide timer functions. The UPD8155C essentially acts as a versatile I/O expander and timer for these older microprocessor systems.

Applications

• Microprocessor-based control systems: Used to expand the I/O capabilities of 8080/8085-based systems in industrial control, instrumentation, and other embedded applications.
• Data acquisition systems: Provides a means to interface with sensors and other data sources for data collection.
• Peripheral device interfacing: Allows microprocessors to communicate with a variety of peripheral devices, such as printers, keyboards, and displays.
• Training and educational platforms: Used in educational kits and training systems for teaching microprocessor interfacing and programming.
• Legacy system maintenance: As a component in older systems that require continued operation and maintenance.

Features

• Three programmable I/O ports: Provides 22 programmable I/O lines that can be configured as inputs or outputs.
• 256 bytes of static RAM: Includes on-chip RAM for data storage and temporary variables.
• 14-bit timer/counter: Features a programmable timer that can be used for generating interrupts, timing events, or counting pulses.
• Interrupt generation: The timer can generate interrupts to signal the microprocessor when a specific time interval has elapsed.
• Single 5V power supply: Operates from a single 5V power source.

Benefits

• Increased I/O capacity: Expands the number of I/O lines available to the microprocessor, allowing it to control more external devices.
• Simplified system design: Integrates I/O ports, RAM, and a timer into a single chip, simplifying the overall system design.
• Flexible I/O configuration: The programmable I/O ports can be configured to meet the specific requirements of the application.
• Timer functionality: The on-chip timer provides a convenient way to generate time delays and interrupts.
• Compatibility: Designed to interface directly with 8080/8085 microprocessors.

Additional Details

The UPD8155C is typically packaged in a 40-pin DIP (Dual In-line Package). It communicates with the microprocessor via the system bus, including address, data, and control lines. The chip is programmed by writing control words to specific address locations, configuring the I/O ports and timer. The static RAM offers a storage area to the microprocessor without needing additional memory devices in many cases.