CMOS Priority Interrupt Controller# CP82C59A Programmable Interrupt Controller (PIC) Technical Documentation
Manufacturer : INTERSIL
## 1. Application Scenarios
### Typical Use Cases
The CP82C59A serves as a programmable interrupt controller in microprocessor-based systems, primarily handling interrupt request management and prioritization. Key applications include:
- Interrupt Vector Generation : Provides appropriate interrupt vectors to the CPU in response to interrupt requests
- Priority Resolution : Manages multiple interrupt sources with programmable priority schemes
- Cascaded Systems : Supports master-slave configurations for expanding interrupt handling capability
- Masking Operations : Enables selective enabling/disabling of individual interrupt lines
### Industry Applications
- Industrial Control Systems : Process control equipment, PLCs, and automation systems
- Telecommunications : Switching equipment, modem controllers, and communication interfaces
- Medical Instrumentation : Patient monitoring systems and diagnostic equipment
- Embedded Systems : Single-board computers, industrial PCs, and microcontroller systems
- Test and Measurement : Data acquisition systems and laboratory instruments
### Practical Advantages and Limitations
Advantages:
- Flexible Programming : Fully programmable interrupt modes and priority schemes
- Cascading Capability : Supports up to 64 interrupt levels in master-slave configuration
- Compatibility : Pin-compatible with industry-standard 8259A devices
- Low Power Consumption : CMOS technology ensures efficient power usage
- Automatic EOI : Supports automatic end-of-interrupt modes
Limitations:
- Legacy Architecture : Designed for older microprocessor architectures (x86, 8086/8088)
- Limited Modern Integration : Often replaced by integrated interrupt controllers in modern processors
- Programming Complexity : Requires careful initialization sequence and mode programming
- Fixed Pin Count : Limited to 8 interrupt request lines without cascading
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Improper Initialization Sequence
- Issue : Failure to follow the required 4-byte initialization command word sequence
- Solution : Implement strict initialization routine with proper timing between command words
Pitfall 2: Interrupt Vector Mismatch
- Issue : Incorrect vector programming leading to wrong interrupt service routine execution
- Solution : Ensure vector addresses align with CPU interrupt vector table
Pitfall 3: Master-Slave Configuration Errors
- Issue : Incorrect cascading in multi-PIC systems causing interrupt loss
- Solution : Properly configure CAS lines and ensure correct slave addressing
### Compatibility Issues
Microprocessor Compatibility:
- Optimal : Intel 8086, 8088, and compatible processors
- Requires Adaptation : Modern processors may need compatibility bridges
- Bus Timing : Verify compatibility with system bus timing specifications
Peripheral Integration:
- DMA Controllers : Requires careful timing coordination with devices like 8237A
- Bus Arbitration : May conflict with other bus masters without proper handshaking
- Clock Synchronization : Ensure clock signals meet setup and hold time requirements
### PCB Layout Recommendations
Power Distribution:
- Use 0.1μF decoupling capacitors placed within 0.5" of VCC pins
- Implement separate analog and digital ground planes with single-point connection
- Ensure adequate power trace width for maximum current requirements
Signal Integrity:
- Route interrupt lines (IR0-IR7) as controlled impedance traces
- Keep CAS lines (CAS0-CAS2) short and matched in length for cascaded configurations
- Maintain proper spacing between high-frequency signals and interrupt lines
Thermal Management:
- Provide adequate copper pour for heat dissipation
- Consider thermal vias under the package for improved heat transfer
- Ensure proper airflow in high-density layouts
## 3. Technical
