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mcpu-verilog-8bitworkshop
Open this project in 8bitworkshop.
This repository also contains some support files to run the CPU using verilator outside the browser.
Memory map
| From | To | Usage |
|---|---|---|
| 0x0000 | 0x3fff | DRAM |
| 0x4000 | 0x7fff | IROM |
| 0x8000 | 0x9fff | VRAM |
Special registers in VRAM
| Address | Name | Usage |
|---|---|---|
| 0x9fff | CTL_CONFIG | Main control/graphics mode select register |
| 0x9ffe | CTL_COLOR0 | Primary fg/bg colors used in 1-bit text/framebuffer modes |
| 0x9ffd | CTL_COLOR1 | Secondary fg/bg colors used in two-color text mode |
| 0x9ffc | CTL_BORDER | Border pattern colors |
| 0x9ffb | CTL_PAGE | Offset in VRAM added to scanout address, to enable scrolling/double buffering. Value is left-shifted 5x before add. |
CTL_CONFIG bits
| Bits | Name | Usage |
|---|---|---|
| 0 | CTL_CONFIG_MODE | if set is fb graphics mode, text mode otherwise |
| 2-1 | CTL_CONFIG_FB_MODE | fb mode: 2 bit framebuffer format, see below |
| 1 | CTL_CONFIG_TEXT_COLOR | text mode: if set uses 2-color mode(highest bit in character byte selects between color0 and color1) |
| 2 | CTL_CONFIG_TEXT_EXTEND | text mode: this bit replaces the already used highest character byte bit when the CTL_CONFIG_TEXT_COLOR bit is set. |
Framebuffer formats:
| Bits | Name | Page size |
|---|---|---|
| 00 | 128x128_4bpp | 8KB/page |
| 01 | 256x256_1bpp | 8KB/page |
| 10 | 128x128_1bpp | 2KB/page |
| 11 | 128x64_4bpp | 4KB/page |
Misc commands
# remove old build artifacts
rm -rf obj_dir irom.hex
# run nanoasm on the program for the instruction ROM
node ~/stuff/mcpu/mcpu_nanoasm/src/asmmain.js ~/stuff/mcpu/mcpu_nanoasm/examples/mcpu_asm.json irom.asm | tee irom.hex
# build the Lua interpreter-wrapped module
./build_and_run.sh mcpu_top.v
# run the module with the test script
./obj_dir/Vmcpu_top test_mcpu_top.lua +verilator+rand+reset+2
# combined full rebuild & run:
clear && node ~/stuff/mcpu/mcpu_nanoasm/src/asmmain.js ~/stuff/mcpu/mcpu_nanoasm/examples/mcpu_asm.json irom.asm > irom.hex && ./build_and_run.sh mcpu_top.v test_mcpu_top.lua
# combined asm re-compile and run:
node ~/stuff/mcpu/mcpu_nanoasm/src/asmmain.js ~/stuff/mcpu/mcpu_nanoasm/examples/mcpu_asm.json irom.asm > irom.hex && ./obj_dir/Vmcpu_top test_mcpu_top.lua +verilator+rand+reset+2