CMOS Asynchronous Communications Element# CP82C50A5 Programmable Communications Interface Technical Documentation
Manufacturer : INTERSIL
## 1. Application Scenarios
### Typical Use Cases
The CP82C50A5 serves as a programmable asynchronous communications interface adapter, primarily functioning as:
- Serial Data Communication Controller : Converts parallel data from microprocessors to serial data streams and vice versa
- Modem Interface Controller : Provides handshake signals and control logic for modem communication
- Data Terminal Equipment (DTE) : Interfaces computers with data communication equipment
- Industrial Serial Port : Manages RS-232/RS-422/RS-485 communication protocols
### Industry Applications
Telecommunications Systems
- Modem banks and communication servers
- Telephone switching equipment
- Network interface cards
Industrial Automation
- PLC (Programmable Logic Controller) communication interfaces
- SCADA (Supervisory Control and Data Acquisition) systems
- Industrial networking equipment
Computer Peripherals
- Serial port expansion cards
- Terminal servers
- Legacy system interface adapters
Embedded Systems
- Microcontroller communication interfaces
- Data acquisition systems
- Remote monitoring equipment
### Practical Advantages and Limitations
Advantages:
- Full Programmable Configuration : All communication parameters (baud rate, data bits, parity, stop bits) are software-configurable
- Multiple Protocol Support : Compatible with RS-232, RS-422, and RS-485 standards
- Hardware Handshake Support : Includes RTS/CTS, DTR/DSR handshake signals
- Low Power Consumption : CMOS technology ensures efficient power usage
- High Reliability : Industrial temperature range (-40°C to +85°C) operation
Limitations:
- Legacy Interface : Limited to traditional serial communication protocols
- Speed Constraints : Maximum baud rate of 1.5 Mbps may be insufficient for modern high-speed applications
- Component Count : Requires external crystal oscillator and supporting passive components
- Software Complexity : Requires detailed initialization and configuration programming
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Improper Clock Configuration
- Issue : Incorrect baud rate generation due to wrong clock frequency selection
- Solution : Use precise 1.8432 MHz or 3.6864 MHz crystal oscillator with proper loading capacitors
Pitfall 2: Signal Integrity Problems
- Issue : Data corruption in long-distance communication
- Solution : Implement proper line drivers/receivers (MAX232, MAX485) for signal conditioning
Pitfall 3: Interrupt Handling Errors
- Issue : Missed data or system lockups due to improper interrupt service routine design
- Solution : Implement robust interrupt handling with proper status register polling
Pitfall 4: Power Supply Noise
- Issue : Communication errors caused by power supply ripple
- Solution : Use decoupling capacitors (100nF ceramic + 10μF tantalum) close to power pins
### Compatibility Issues with Other Components
Microprocessor Interfaces
- 8-bit Microprocessors : Direct compatibility with 8085, Z80, 6800 families
- 16/32-bit Processors : Requires additional glue logic for bus interface
- Modern Microcontrollers : May need level shifters and timing adjustment circuits
Voltage Level Compatibility
- TTL/CMOS Levels : Direct interface for digital logic (0-5V)
- RS-232 Levels : Requires external level converters (±3V to ±15V)
- RS-485 Differential : Needs external transceivers
### PCB Layout Recommendations
Power Distribution
- Place decoupling capacitors within 5mm of VCC pins
- Use separate ground planes for analog and digital sections
- Implement star-point grounding for noise
