Design and Implementation Of AMBA Wrapper for Leon3 Processor

Abstract

The effort to implement a single chip system from scratch is enormous and only a few companies have the needed competency in all design areas. In most cases, designers will have to use Intellectual Property (IP) blocks or Virtual Components (VCs). IP blocks are predefined, large grained logic blocks, (such as processors, memories, and peripherals) whose function has been precisely specified. They can be developed inhouse or originate from external vendors. When IP blocks become widely available, the design focus will shift to reuse. Chip design is becoming much more a matter of design composition than of design creation. These compositional or reuse based design methodologies will be the issue addressed by System on Chip (SoC) designers. To attach an IP with one of the buses in the design, the designer has to create an interface for it. To ease this task, the FPGA vendors provide the facility for automatic generation of interfaces for custom IPs. This type of support is primarily available for proprietary processors like Microblaze. On the other hand no such facility exists for open source processors like Leon. AMBA is a standard bus architecture which is widely used for on-chip communication purpose between different components of the chip.Different components on the chip has different input and outputs pins and AMBA BUS have standard pin configuration. AMBA bus handles 32-bits addressing with 32-bits data size, it also supports different signals like reset, clock, interrupts, enable, write data and read data signals. So we need to create a wrapper for different components, so that they can easily communicate with each other via AMBA bus. For example in my project i have interfaced UART which is 8-bit wide and having different pins like chip select, reset, clock, interrupt signals. So i have created a AMBA APB wrapper for UART, by interfacing the different signals of the APB and UART as per requriment.