CMOS Bus Arbiter# CP82C89 Technical Documentation
Manufacturer : HARRIS
## 1. Application Scenarios
### Typical Use Cases
The CP82C89 is a high-performance bus arbiter designed for multiprocessor systems utilizing the Multibus architecture. Primary applications include:
- Multiprocessor arbitration in industrial control systems
- Bus contention management in telecommunications equipment
- Memory access coordination between multiple CPUs
- I/O resource sharing in distributed computing environments
### Industry Applications
- Industrial Automation : Coordinates multiple processors in PLCs and distributed control systems
- Telecommunications : Manages bus access in switching equipment and network controllers
- Military/Aerospace : Provides reliable arbitration in mission-critical systems (operates over extended temperature ranges)
- Medical Equipment : Ensures deterministic access in multi-processor diagnostic systems
- Data Acquisition : Coordinates multiple processors in high-speed measurement systems
### Practical Advantages
- High-speed operation with typical propagation delays of 35ns
- Multiple priority schemes including parallel, rotating, and serial priority
- Low power consumption CMOS technology (typically 85mA operating current)
- Wide operating temperature range (-40°C to +85°C)
- Built-in bus timeout capability prevents bus lockup conditions
### Limitations
- Legacy architecture primarily designed for Multibus systems
- Limited to 16 bus masters maximum without additional circuitry
- Requires external crystal for timing reference (typically 10MHz)
- Not compatible with modern high-speed bus architectures
- Limited documentation and support due to legacy status
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Improper Clock Configuration
- Issue : Unstable operation due to incorrect clock signal quality
- Solution : Use crystal oscillator with proper load capacitors and keep clock traces short (<2cm)
Pitfall 2: Bus Contention During Power-up
- Issue : Multiple processors attempting bus access simultaneously during initialization
- Solution : Implement power-on reset circuit with minimum 100ms delay before enabling bus requests
Pitfall 3: Ground Bounce in High-Speed Systems
- Issue : Signal integrity problems at maximum clock frequencies
- Solution : Use decoupling capacitors (0.1μF ceramic) within 5mm of each power pin
### Compatibility Issues
Processor Compatibility
- Well-suited for : Intel 8086/8088, 80186, 80286 processors
- Requires interface logic for : Motorola 68000 series, modern RISC processors
- Incompatible with : PCI, USB, or other modern bus architectures without bridge chips
Voltage Level Considerations
- Input compatibility : TTL and 5V CMOS levels
- Output drive : Standard TTL compatible (sinks 4mA, sources 400μA)
- Not compatible with : 3.3V or lower voltage systems without level shifting
### PCB Layout Recommendations
Power Distribution
- Use star topology for power distribution to minimize ground loops
- Implement separate analog and digital ground planes with single-point connection
- Place bulk decoupling (10μF tantalum) near power entry points
Signal Integrity
- Route critical control signals (BPRN, BPRO, BUSY) with matched lengths (±5mm)
- Maintain minimum 3X trace width spacing between high-speed signals
- Use 45-degree corners instead of 90-degree turns for all signal traces
Thermal Management
- Provide adequate copper pour around package for heat dissipation
- Ensure minimum 2mm clearance from other heat-generating components
- Consider thermal
