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# J-core j1 for Lattice ice40 FPGA, with GHDL build/test script

This is a stripped-down build of https://j-core.org j2 processor which
is instruction set compatibile with the full j2 but has no I/O devices,
DRAM controller or SMP support.

Install https://github.com/ghdl/ghdl and run ./ghdl_lattice.sh to build and
simulate this CPU running a test rom. (If it prints the C0 line all instruction
tests passed.) See the testrom/ directory for ROM source, for bare metal
elf toolchain build instructions see:
  http://lists.j-core.org/pipermail/j-core/2019-October/000867.html

A working ICE40 UltraPlus5k bitstream was produced from this source via
Lattice's Synplify+IceCube2 toolchain. It's also been tested with GHDL, NVC,
Xilinx WebPack ISE, and Vivado.

We are working to get a fully open source VHDL toolchain (built from
ghdl+ghdlsynth+yosys+abc) creating bitstreams from that (it doesn't yet).
For build instructions for that see:
  http://lists.j-core.org/pipermail/j-core/2019-November/000868.html