Simple 8-bit processor with an 8-bit data bas, a 16-bit address bus and 8 in/out ports. Code and data is shared (Von Neumann architecture).
hellorld.mp4
godjul.mp4
The last 16 bytes of memory are used for storing data and address registers (instruction registers) in addition to temporary storage during microcode steps.
8-bit data registers: a, b, c and d
16-bit address registers: i and j
8-bit special registers: sp
Two 8-bit registers LS and RS makes up the operands to the ALU. Neither are accessible from software. Two ROMs makes up a lookup table for different ALU operation. A 4-bit flag register is available for storing zf, cf, of and sf.
Two ROMs together with a 4-bit step counter, an 8-bit opcode register and the flags register makes up a lookup table for different microcode steps for different instructions. The step counter is cleared on reset.
Two 8-bit register ML and MH makes up the 16-bit address bus. Neither are accessible from software. The registers are cleared on reset making program execution start at 0x0000.
The high part of the stack is locked at 0xff. The low part is loaded by setting the sp instruction register. The stack grows upwards towards 0xffff. Usually the sp is loaded with 0xff making the first push at 0xff00.
One control signal toggles if the address bus is based on ML/MH or the low 4-bits of the constant register or:ed by 0xfff0. This is used to address the instruction registers during microcode steps.
0x0000 - 0x7fff: ROM
0x8000 - 0xfff0: RAM
0xfff0 - 0xffff: RAM containing instruction registers
The input clock source is divided into two equally long phases named setup and execute. The setup phase settles the control signals and the execute phase latches the input source (the data bus for example).
The data bus is pulled high so if nothing is asserted then 0xff will be read.
Requires that the bleh_instructions.asm customasm ruledef file exists:
./compile_and_run.zsh customasm.c
Then compile your program using customasm, for example:
customasm -q ./software/test_lcd.asm --print --format intelhex
Using the arduino boot device, connect a serial monitor and paste Intel Hex format of the program.
./compile.zsh emulator.c
Requires that the control and ALU ROM binaries are built:
./compile_and_run.zsh control.c && ./compile_and_run.zsh alu.c
Then compile your program using customasm:
customasm <PROGRAM TO RUN>.asm --format binary --output <PROGRAM TO RUN>.bin
Then finally run the program using the emulator:
./bin/emulator <PROGRAM TO RUN>.bin [CLOCK FREQUENCY IN HZ]