grom8
grom8 copied to clipboard
Published
20 hours ago •
mmicko
mmicko
GROM-8 CPU
Grom-8 FPGA
This CPU implementation is made for purely educational purposes, in order to learn various constructs in Verilog. It is far from perfect, but includes all needed features one CPU needs.
GROM-8 is simple 8-bit CPU, with :
- 4 general purpose registers
- 12 bit address bus and PC (program counter)
- Code and data segment registers (CS,DS) (4 bit)
- Stack pointer (SP) (12 bit)
- 8-bit ALU with C-carry, Z-zero and S-sign flags
Instruction set
| 7..4 | 3..2 | 1..0 | 2nd | Instruction |
|---|---|---|---|---|
| 0000 | dst | src | MOV dst, src | |
| 0001 | 00 | reg | ADD reg | |
| 0001 | 01 | reg | SUB reg | |
| 0001 | 10 | reg | ADC reg | |
| 0001 | 11 | reg | SBC reg | |
| 0010 | 00 | reg | AND reg | |
| 0010 | 01 | reg | OR reg | |
| 0010 | 10 | reg | NOT reg | |
| 0010 | 11 | reg | XOR reg | |
| 0011 | 00 | reg | INC reg | |
| 0011 | 01 | reg | DEC reg | |
| 0011 | 10 | reg | CMP reg | |
| 0011 | 11 | reg | TST reg | |
| 0100 | 00 | 00 | SHL | |
| 0100 | 00 | 01 | SHR | |
| 0100 | 00 | 10 | SAL | |
| 0100 | 00 | 11 | SAR | |
| 0100 | 01 | 00 | ROL | |
| 0100 | 01 | 01 | ROR | |
| 0100 | 01 | 10 | RCL | |
| 0100 | 01 | 11 | RCR | |
| 0100 | 10 | reg | PUSH reg | |
| 0100 | 11 | reg | POP reg | |
| 0101 | dst | src | LOAD dst, [src] | |
| 0110 | dst | src | STORE [dst], src | |
| 0111 | 00 | reg | MOV CS, reg | |
| 0111 | 01 | reg | MOV DS, reg | |
| 0111 | 10 | 00 | PUSH CS | |
| 0111 | 10 | 01 | PUSH DS | |
| 0111 | 10 | 10 | ??? | |
| 0111 | 10 | 11 | ??? | |
| 0111 | 11 | 00 | ??? | |
| 0111 | 11 | 01 | ??? | |
| 0111 | 11 | 10 | RET | |
| 0111 | 11 | 11 | HLT | |
| 1000 | 00 | 00 | val | JMP val |
| 1000 | 00 | 01 | val | JC val |
| 1000 | 00 | 10 | val | JNC val |
| 1000 | 00 | 11 | val | JM val |
| 1000 | 01 | 00 | val | JP val |
| 1000 | 01 | 01 | val | JZ val |
| 1000 | 01 | 10 | val | JNZ val |
| 1000 | 01 | 11 | val | ??? |
| 1000 | 10 | 00 | val | JR val |
| 1000 | 10 | 01 | val | JRC val |
| 1000 | 10 | 10 | val | JRNC val |
| 1000 | 10 | 11 | val | JRM val |
| 1000 | 11 | 00 | val | JRP val |
| 1000 | 11 | 01 | val | JRZ val |
| 1000 | 11 | 10 | val | JRNZ val |
| 1000 | 11 | 11 | val | ??? |
| 1001 | high | low | JUMP addr | |
| 1010 | high | low | CALL addr | |
| 1011 | high | low | MOV SP,addr | |
| 1100 | xx | reg | val | IN reg,[val] |
| 1101 | xx | reg | val | OUT [val],reg |
| 1110 | xx | 00 | val | MOV CS,val |
| 1110 | xx | 01 | val | MOV DS,val |
| 1110 | xx | 10 | val | ??? |
| 1110 | xx | 11 | val | ??? |
| 1111 | 00 | reg | val | MOV reg, val |
| 1111 | 01 | reg | val | LOAD reg, [val] |
| 1111 | 10 | reg | val | STORE [val], reg |
| 1111 | 11 | xx | val | ??? |
mmicko