CMOS Priority Interrupt Controller # CP82C59AZ Programmable Interrupt Controller (PIC) Technical Documentation
*Manufacturer: INTERSIL*
## 1. Application Scenarios
### Typical Use Cases
The CP82C59AZ is a CMOS version of the industry-standard 8259A Programmable Interrupt Controller, primarily employed in microprocessor-based systems to manage interrupt requests (IRQs). Key use cases include:
- Microprocessor Interrupt Management : Handles up to 8 interrupt requests for processors like Intel 8085, 8086, 8088, and compatible microprocessors
- Cascaded Interrupt Systems : Supports master-slave configurations to manage up to 64 interrupt levels through cascading multiple PICs
- Priority Resolution : Automatically resolves priority among multiple interrupting devices using fully nested mode
- Edge/Level Triggering : Configurable for edge-triggered or level-triggered interrupt inputs
### Industry Applications
- Industrial Control Systems : Process control, automation systems requiring real-time interrupt handling
- Medical Equipment : Patient monitoring systems, diagnostic equipment with multiple sensor inputs
- Telecommunications : Switching systems, modem controllers, communication interfaces
- Embedded Systems : Single-board computers, industrial PCs, instrumentation controllers
- Legacy Systems : Maintenance and repair of older industrial and military systems
### Practical Advantages and Limitations
Advantages:
- Reduced Processor Overhead : Offloads interrupt management from main processor
- Flexible Configuration : Fully programmable interrupt modes and priorities
- CMOS Technology : Low power consumption (typically 10mA active, 500μA standby)
- Wide Voltage Range : Operates from 4.5V to 5.5V supply
- Temperature Range : Commercial (0°C to +70°C) and industrial (-40°C to +85°C) versions available
Limitations:
- Legacy Architecture : Limited to 8 interrupt lines without cascading
- Fixed Priority Scheme : Basic priority resolution may not suit all applications
- Initialization Complexity : Requires careful programming of multiple control registers
- Compatibility Issues : May require glue logic with modern processors
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Improper Initialization Sequence
- Issue : Failure to follow exact initialization sequence can cause unpredictable behavior
- Solution : Strictly adhere to ICW1-ICW4 initialization command word sequence with proper timing
Pitfall 2: Interrupt Vector Mismatch
- Issue : Incorrect vector address programming leads to wrong interrupt service routine execution
- Solution : Ensure vector addresses align with processor's interrupt vector table
Pitfall 3: Master/Slave Configuration Errors
- Issue : Incorrect CAS line connections in cascaded systems
- Solution : Verify CAS0-CAS2 connections and SP/EN pin configuration
### Compatibility Issues
Processor Compatibility:
- Direct compatibility with 8086/8088 family
- Requires additional logic for modern processors
- May need level shifting for 3.3V systems
Bus Interface:
- Compatible with 8-bit data buses
- Requires buffering for high-speed systems
- Watch for timing constraints with faster processors
Interrupt Sharing:
- Limited support for shared interrupts
- Requires external logic for proper level-triggered sharing
### PCB Layout Recommendations
Power Distribution:
- Use 0.1μF decoupling capacitors close to VCC and GND pins
- Implement star grounding for analog and digital sections
- Ensure adequate power plane coverage
Signal Integrity:
- Route IRQ lines with controlled impedance
- Keep interrupt lines away from clock and high-speed signals
- Use series termination for long traces
Thermal Management
