eSi-RISC is a configurable CPU architecture from EnSilica

EnSilica

EnSilica is a design services and IP core company based in Wokingham, UK. It is known for its eSi-RISC configurable microprocessor cores for System-on-a-chip designs...

. It is currently available in three different implementations: the eSi-1600, eSi-3200 and eSi-3250. The eSi-1600 features a 16-bit

16-bit

-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...

 data-path, while the eSi-3200 and eSi-3250 feature 32-bit

32-bit

The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....

 data-paths. Each of these processors are licensed as soft IP cores, suitable for integrating in to both ASIC

ASIC

ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...

s and FPGAs.

Architecture

The main features of the eSi-RISC architecture are as follows:

• RISC-like load/store architecture.
• Configurable 16 or 32-bit data-path.
• Instructions are encoded in either 16 or 32-bits.
• 8, 16 or 32 general purpose registers.
• 0, 8, 16 or 32 vector registers.
• 0 to 8 accumulators.
• Up to 32 external interrupts.
• Configurable instruction set including support for integer, floating-point and fixed-point arithmetic.
• Optional support for user-defined instructions.
• Optional caches (Configurable size and associtivity) and MMU
  MMU
  MMU may refer to:* Manchester Metropolitan University in England* Manned Maneuvering Unit, a NASA rocket pack that snaps onto the back of a spacesuit* Marymount University, a Catholic university in Arlington, Virginia...
  
  .
• AMBA
  Advanced Microcontroller Bus Architecture
  The Advanced Microcontroller Bus Architecture is used as the on-chip bus in system-on-a-chip designs. Since its inception, the scope of AMBA has gone far beyond microcontroller devices, and is now widely used on a range of ASIC and SoC parts including applications processors used in modern...
  
   AXI, AHB and APB bus interfaces.
• Memory mapped I/O.
• 5-stage pipeline.
• Hardware JTAG
  JTAG
  Joint Test Action Group is the common name for what was later standardized as the IEEE 1149.1 Standard Test Access Port and Boundary-Scan Architecture. It was initially devised for testing printed circuit boards using boundary scan and is still widely used for this application.Today JTAG is also...
  
   debug.

While there are many different 16 or 32-bit Soft microprocessor

Soft microprocessor

A soft microprocessor is a microprocessor core that can be wholly implemented using logic synthesis...

 IP cores available, eSi-RISC is the only architecture licensed as an IP core that has both 16 and 32-bit implementations.

Unlike in other RISC architectures supporting both 16 and 32-bit instructions, such as ARM/Thumb or MIPS/MIPS-16, 16 and 32-bit instructions in the eSi-RISC architecture can be freely intermixed, rather than having different modes where you are executing either all 16-bit instructions or all 32-bit instructions. This helps improve code density without compromising performance.

eSi-RISC includes support for Multiprocessing

Multiprocessing

Multiprocessing is the use of two or more central processing units within a single computer system. The term also refers to the ability of a system to support more than one processor and/or the ability to allocate tasks between them...

. Implementations have included up to seven eSi-3250's on a single chip..

Toolchain

The eSi-RISC toolchain is based on combination of a port of the GNU toolchain

GNU toolchain

The GNU toolchain is a blanket term for a collection of programming tools produced by the GNU Project. These tools form a toolchain used for developing applications and operating systems....

 and the Eclipse IDE

Integrated development environment

An integrated development environment is a software application that provides comprehensive facilities to computer programmers for software development...

. This includes:

• GCC
  GNU Compiler Collection
  The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...
  
   - C/C++ compiler.
• Binutils - Assembler, linker and binary utilities.
• GDB - Debugger.
• Eclipse - Integrated Development Environment.

The C library is Newlib

Newlib

Newlib is a C standard library implementation intended for use on embedded systems. It is a conglomeration of several library parts, all under free software licenses that make them easily usable on embedded products....

 and the C++ library is Libstdc++. Ported RTOSes include MicroC/OS-II

MicroC/OS-II

MicroC/OS-II , is a low-cost priority-based pre-emptive real-time multitasking operating system kernel for microprocessors, written mainly in the C programming language...

, FreeRTOS

FreeRTOS

FreeRTOS is a real-time operating system for embedded devices, being ported to several microcontrollers. It is distributed under the GPL with an optional exception...

and ERIKA Enterprise.

External links

• EnSilica's eSi-RISC Homepage