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{{Short description|Configurable CPU architecture}}
{{Use dmy dates|date=July 2014}}
{{refimprove|date=December 2009}}
{{lowercase}}
{{Infobox CPU architecture
| name = eSi-RISC
| designer = eSi-RISC
| bits = 16-bit/32-bit
| introduced = 2009
| version =
| design = RISC
| type = [[Load–store]]
| encoding = Intermixed 16 and 32-bit
| branching = Compare and branch and condition code
| endianness = Big or little
| extensions = User-defined instructions
| registers = 8/16/32 General Purpose, 8/16/32 Vector
}}
'''eSi-RISC''' is a configurable [[CPU]] architecture. It is available in five implementations: the eSi-1600, eSi-1650, eSi-3200, eSi-3250 and eSi-3264.<ref>[http://www.electronicsweekly.com/Articles/2009/11/17/47447/ensilicas-esi-risc-soft-processor-cores-are-aimed-at-socs.htm] Electronics Weekly, 17 November 2009</ref> The eSi-1600 and eSi-1650 feature a [[16-bit]] data-path, while the eSi-32x0s feature [[32-bit]] data-paths, and the eSi-3264 features a mixed 32/64-bit datapath. Each of these processors is licensed as soft [[IP core]]s, suitable for integrating into both [[Application-specific integrated circuit|ASIC]]s and [[FPGA]]s.<ref>[http://www.eetimes.eu/design/221800121]{{Dead link|date=July 2019 |bot=InternetArchiveBot |fix-attempted=yes }} EE Times, 17 November 2009</ref>

== Architecture ==
{{prose|section|date=May 2019}}
The main features of the eSi-RISC architecture are:<ref>[https://www.esi-risc.com/risc-ip/esi-3250/] eSi-RISC eSi-3250 Technical Overview</ref>
[[Image:eSi-3250.png|thumb|eSi-3250 SoC architecture]]
* [[RISC]]-like load/store architecture.
* Configurable 16-bit, 32-bit or 32/64-bit data-path.
* Instructions are encoded in either 16 or 32-bits.
* 8, 16 or 32 general purpose registers, that are either 16 or 32-bits wide.
* 0, 8, 16 or 32 vector registers, that are either 32 or 64-bits wide.
* Up to 32 external, vectored, nested and prioritizable interrupts.
* Configurable instruction set including support for integer, floating-point and fixed-point arithmetic.
* [[SIMD]] operations.
* Optional support for user-defined instructions, such as cryptographic acceleration .<ref>[http://www.electronicsweekly.com/news/components/microprocessors-and-dsps/ensilica-designs-secure-processor-with-kili-technology-2013-10/] Electronics Weekly, 2013</ref>
* Optional caches (Configurable size and associativity).
* Optional [[Memory management unit|MMU]] supporting both memory protection and dynamic address translation.
* [[Advanced Microcontroller Bus Architecture|AMBA]] AXI, AHB and APB bus interfaces.
* Memory mapped I/O.
* 5-stage pipeline.
* Hardware [[JTAG]] debug.

While there are many different 16 or 32-bit [[Soft microprocessor]] 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 either all 16-bit instructions or all 32-bit instructions are executed. This improves code density without compromising performance. The 16-bit instructions support two register operands in the lower 16 registers, whereas the 32-bit instructions support three register operands and access to all 32 registers.

eSi-RISC includes support for [[Multiprocessing]]. Implementations have included up to seven eSi-3250's on a single chip.<ref>[http://www.design-reuse.com/news/26334/ensilica-posedge-deal.html] Design & Reuse, 2011</ref>

== Toolchain ==

The eSi-RISC toolchain is based on combination of a port of the [[GNU toolchain]] and the [[Eclipse ide|Eclipse]] [[Integrated development environment|IDE]].<ref>[http://www.ensilica.com/pdfs/EnSilica%20A4_Flyer_eSi-RISC%20IP.PDF] {{Webarchive|url=https://web.archive.org/web/20120228234558/http://www.ensilica.com/pdfs/EnSilica%20A4_Flyer_eSi-RISC%20IP.PDF |date=28 February 2012 }} EnSilica, 2009</ref> This includes:

* [[GNU Compiler Collection|GCC]] – C/C++ compiler.
* [[Binutils]] – Assembler, linker and binary utilities.
* [[GDB]] – Debugger.
* [[Eclipse ide|Eclipse]] – Integrated Development Environment.

The C library is [[Newlib]] and the C++ library is [[Libstdc++]]. Ported [[RTOS]]es include [[MicroC/OS-II]], [[FreeRTOS]], [[ERIKA Enterprise]]<ref>[http://www.electronicsweekly.com/Articles/2010/10/07/49603/open-source-rtos-targets-automotive-systems.htm] Electronics Weekly, 2010,</ref> and [[Phoenix-RTOS]]<ref>[https://web.archive.org/web/20131211141823/http://www.cambridgenetwork.co.uk/news/phoenix-ports-phoenix-rtos-to-ensilica-s-esi-risc/] Cambridge Network 2013</ref>

==References==
{{reflist|2}}

==External links==
* [http://www.esi-risc.com/ eSi-RISC homepage]

{{RISC-based processor architectures}}

{{DEFAULTSORT:Esi-Risc}}
[[Category:Soft microprocessors]]

ESi-RISC - Revision history

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