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Game Boy Classic fully functional FPGA implementation from scratch


sudo apt-get install iverilog gtkwave

##Compiling code cd sim/

make compile

##Running a simulation

cd sim/

make run

Once the simulation completes, the following ASCII files are generated under the sim/ folder:

  • pgb_cpu.log : Z80 macro instructions and their corresponding micro-code flows
  • pgb_gpu.log: GPU micro code dump
  • generated_frames/*.ppm : PPM representation of the video buffer frames at the time the simulation ended. (Open it with gimp)
  • papi_vram_8000_8fff.dump : Memory dump for the Tile set region 0
  • papi_vram_9800_9bff.dump : Memory dump for the Tile map region 0
  • tb_simple_dzcpu : Simulation testbench executable

Simulations will not automatically generate a VCD dump file. To generate a VCD dump do:

make DUMPTYPE=vcd

##Simulation Options To control additional simulation options, use the SIMFLAGS flag. Valid values are:

  • -DSTOP_AFTER_FIRST_FRAME : The simulation will stop once the first frame has been generated under the sim/generated_frames/ folder
  • -DENABLE_CPU_LOG : Enables pgb_cpu.log generation (enabled by default)
  • -DENABLE_GPU_LOG : Enables pgb_cpu.log generation (enabled by default)
  • -DCARTRIGDE_DUMP_PATH : When LOAD_CARTRIDGE_FROM_FILE is set, then this flag specifies the path to the dump file
  • -DSKIP_BIOS : Skips the BIOS code, first 256 instructions, effectively jumping directly to 0x100
  • -DDISABLE_CPU: Disables the CPU from running
  • -DVMEM_DUMP_PATH: When LOAD_VMEM_DUMP is set, then this flag specifies the path to the VMEME dump file.
  • -DSIMULATION_TIME_OUT: Specify a simulation timeout in nanoseconds Example:

The following command will stop the simulation after the first frame, will generate GPU log, but will not generate CPU log.


The following command will simulate RTL using a cartrigde file:

make SIMFLAGS=" -DCARTRIGDE_DUMP_PATH='\"resources/tetris.dump\"'"

The following command will disable the CPU and load VMEM data from a dump file:

make SIMFLAGS="-DDISABLE_CPU -DVMEM_DUMP_PATH='\"resources/tetris_vmem_8000_9fff.dump\"' -DENABLE_GPU_LOG -DSTOP_AFTER_FIRST_FRAME"

##Looking at simulation results

cd sim/

make view

##Cleaning up simulation files. This also erases the vcd and the log files!

make clean

##Installing a game boy assembly

RGBDS is a great gameboy assembly (

To install it do:

git clone

cd rgbds

sudo apt-get install bison flex


sudo make install

To compile an assebly program called test_INCr_b.asm do:

rgbasm -o test_INCr_b.obj test_INCr_b.asm

rgblink -m -n test_INCr_b.sym -o test_INCr_b.obj

The use hexdump to get the ASCII hex dump to load into the RTL simulation:

hexdump -v > test_INCr_b.hex