J2 Downloads


FPGA RTL is distributed under Berkeley Software Distribution (BSD) License. RTL build tools written in Perl, Clojure, and C/C++ is distributed under GNU L2 Public License.


1. J2 Initial RTL Release: Contains {cpu, ddrc, uart}.

J2 code follows Jiri Gaisler’s VHDL 2 process model, as used in the Leon core, to improve the readability of VHDL code over the “data flow” method, as specified in the document http://www.gaisler.com/doc/vhdl2proc.pdf. Jeff Dionne, Geoff Salmon and Jen McCann, the original developers of J2 core created various utilities in process (e.g. “.vhd” files). Please download Item #3 which shows how to build the VHDL into a Xilinx bitstream.

2. Recipe — How to Run J2 Bitstream+Linux Binary on LX9 Microboard 

After booting the latest vmlinux shows the following:


We would like to thank the engineers of Smart Energy Instruments.

3. Recipe — How to Build J2 from RTL: This document contains how to build RTL, Downloads Item #1, into a Xilinx Bitstream.

An old reliable friend has told me that he was able to download and build this RTL. When he tried to get the Bitstream working he was not able to…  Folks from SEI plans to fix the issue. We though that it would be a good idea to start the downloads of #1 and #3 first because it will take about a week before a LX9 Microboards arrive for most of the recipients.

4. J2 Bitstream for LX9 Microboard: Contains {cpu, ddrc, uart}.

5. J2 uClinux for Lx9 Microboard: Vmlinux with ramfs. The ramfs is used to boot up Linux.

6. J2 Dhrystone Log on Lx9 Microboard: Contains log from running J2 on uClinux on LX9 Microboard.

We included Drystone 2.1 in the directory which shows the following numbers:

      Dhrystones per Second:                      6042.3 

VAX Drystone MIPS = 1757. J2 shows 6042.3 / 1757 = 3.44 MIPS. An insider engineer in Tokyo told 0pf that the LX9 Microboard J2 is running at the 33MHz. Clocks per Instruction (CPI) = 9.59. Even though this is the most underwhelming figure for today’s 32b processor, the author is actually impressed with combination of J2 CPU, DDR controller and DDR all running at 33MHz. This J2 does not have internal RAM nor cash and solely running on DDR. Every instruction and data access translates to a DDR access. DDR is running at 33MHz.

7. J2 Bitstream for LX9 Numato Board  (Work in Progress): LX9 Numato board contains SD file socket and no ethernet port. LX9 board bitstream is expected to contain {cpu, ddrc, uart}.


8. J2 Patches for LX9 Numato Board uClinux  (Work in Progress): LX9 Numato board can do more things Linux since it has SD file system.

9. uClinux J2 Patches: Specific patches to J2.

We will keep you updated as we make more progress.


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