Introduction
As SoCs evolve to support a growing range of memory interfaces, designers are faced with the challenge of balancing integration complexity, pin efficiency, and performance scalability. Traditionally, implementing both xSPI (JESD251) for boot and eMMC 5.1 for high-speed storage required separate PHYs, leading to increased silicon area, power consumption, and I/O overhead.
Arasan’s xSPI/eMMC5.1 PHY addresses this challenge by integrating two distinct PHY layers into a single unified IP. The solution provides protocol flexibility, optimized area utilization, and reduced pin count, making it a highly efficient choice for SoCs requiring both boot and storage capabilities within embedded platforms.
Architecture Overview
The xSPI/eMMC5.1 PHY is designed as a dual-mode physical layer with shared I/O and analog front-end circuitry. At its core, the architecture incorporates:
- Shared PHY Resources: One I/O pad set serves both interfaces.
- Configurable Switching: Protocol selection via hardware control signals or software programming.
- Built-in MUX Logic: Ensures seamless interface switching without external multiplexers.
This unified architecture reduces pin usage, silicon area, and design complexity, while maintaining full compliance with JEDEC standards:
- JESD251 for xSPI
- eMMC 5.1 for high-speed NAND storage
Performance Highlights
- eMMC 5.1 Mode
- Supports HS400 operation with DDR clock at 200 MHz
- Optimized for high-throughput storage applications
- xSPI Mode
- Supports xSPI-400 with DDR clock at 200 MHz
- Provides reliable boot-time execution-in-place (XiP) and high-speed flash access
I/O and DLL Features
The PHY integrates advanced I/O design features to ensure high reliability across process, voltage, and temperature (PVT) variations:
- Analog DLL (Delay Locked Loop) for generating PVT-independent clock delays
- Transmitter Support:
- Push-pull mode with selectable drive strengths (50Ω, 33Ω, 66Ω, 100Ω, 40Ω)
- Open-drain mode for compatibility with shared bus environments
- Differential Receiver for superior noise immunity in high-speed operations
Test and Debug Features
To enhance design validation and silicon bring-up, the PHY includes comprehensive testability features:
- DC Testing of I/O pads
- Built-in Self-Test (BIST) for PHY-level verification
- DLL Output Phase Measurement for precise timing validation
- DC Scan Support for structural test coverage
These features help accelerate post-silicon debug, validation, and production testing.
Applications
The xSPI/eMMC5.1 PHY is particularly suited for embedded SoC platforms where both boot functionality and high-speed storage are required:
- Mobile SoCs: Boot from xSPI NOR flash, operate storage through eMMC 5.1
- Automotive ECUs: Efficiently integrate boot and storage within constrained silicon area
- Consumer Devices: Smartphones, tablets, smart appliances
- Industrial and IoT Systems: Compact controllers requiring cost-sensitive integration
Benefits
By combining xSPI and eMMC PHYs into a single IP, SoC designers gain:
- Reduced Pin Count: Shared I/O interface lowers package complexity
- Lower Area Footprint: Elimination of redundant PHY blocks
- Design Flexibility: Configurable switching between protocols
- Time-to-Market Advantage: Simplified integration and faster SoC bring-up
Conclusion
Arasan’s xSPI/eMMC5.1 PHY offers a strategic integration path for SoC designers needing both boot-time xSPI flash access and high-speed eMMC storage. With its dual-mode capability, JEDEC-compliance, advanced I/O design, and extensive test features, the IP delivers a scalable and efficient solution for modern SoCs.
This unified PHY is not just a cost and area optimization—it is a foundation for next-generation embedded platforms that demand performance, reliability, and flexibility.