jordan336 / tt03-toy-cpu

Toy CPU is an 8 bit toy CPU for the Tiny Tapeout project.

Toy CPU

Toy CPU is an 8 bit toy CPU for the Tiny Tapeout project.

I/O Interface

#	Input	Output
0	clk	data_out[0]
1	rst	data_out[1]
2	instruction[0]	data_out[2]
3	instruction[1]	data_out[3]
4	instruction[2]	data_out[4]
5	instruction[3]	data_out[5]
6	instruction[4]	data_out[6]
7	instruction[5]	data_out[7]

ISA

Opcode	Mnemonic	Name	Description
000	DISP	Display	data_out = reg[src_a]
001	ADD	Add	reg[dest] = reg[src_a] + reg[src_b]
010	ADD_I	Add (immediate)	reg[dest] = reg[src_a] + imm
011	AND	And	reg[dest] = reg[src_a] & reg[src_b]
100	AND_I	And (immediate)	reg[dest] = reg[src_a] & imm
101	OR	Or	reg[dest] = reg[src_a] | reg[src_b]
110	OR_I	Or (immediate)	reg[dest] = reg[src_a] | imm
111	STRE	Store	reg[dest] = imm

Instruction format

Instructions are passed using the upper 6 bits of the inputs. Depending on the opcode, the full instruction with opcode and all arguments is passed using one, two, or three 6 bit instruction words.

Word	Input [7:5]	Input [4:2]	Input [1]	Input [0]
0	opcode[2:0]	src_a[2:0]	rst	clk
1	dest[2:0]	src_b[2:0] or imm[7:5]	rst	clk
2	{X,imm[4:3]}	imm[2:0]	rst	clk

Opcode	Mnemonic	Number of Instruction Words
000	DISP	1
001	ADD	2
010	ADD_I	3
011	AND	2
100	AND_I	3
101	OR	2
110	OR_I	3
111	STRE	3

Start input

After exiting reset, the Toy CPU looks for a start input to begin processing the instruction stream. The start input is all 1s in the 6 bit instruction word (0x3F). After sampling the start sequence, the CPU will interpret the next 6 bit instruction word as the first word in the instruction stream.

What is Tiny Tapeout?

TinyTapeout is an educational project that aims to make it easier and cheaper than ever to get your digital designs manufactured on a real chip!

Go to https://tinytapeout.com for instructions!