683 Tiny Turing Machine :: Quicker, easier and cheaper to make your own chip!

This project implements a Turing Machine on an ASIC with the following features:

8-bit tape with configurable wrap-around mode
4 states (S0-S3) with unary alphabet ( Blank/0 and 1)
State Transition Table (STT) with 4 banks:
- Bank 0: Unary Incrementer - Adds one "1" to a string of ones
- Bank 1: Bit Flipper - Inverts all bits from left to right
- Bank 2: Wall-E - Carries Bits from right side to left bound
- Bank 3: Custom - User-configurable STT

The machine operates in 5 distinct modes:

Two 8-bit outputs are available:

Status format (8 bits):

Head position: The status output can be switched to a (one hot) decoded head position output by setting ui_in[0]=1.

Swap control: ui_in[2]=1 swaps the outputs.

Reset with all inputs low: ui_in = 00000000
- Loads Bank 0 (Unary Incrementer) preset
- Initial tape: 11100000 (three 1s on left)
- Head at position 0 (leftmost)
- State 0
Clock slowly (manual or low frequency)
- Observe uo_out (tape) changing
- Expected behavior:
  - Head moves right through the 1s
  - Finds first 0, writes 1
  - Result: 11110000 (four 1s)
  - Machine halts at right boundary
Observe outputs:
- uo_out: Shows tape pattern (LEDs on bits 7-4)
- uio_out[7:5]: Mode (should be 3=RUN, then 4=HALT)
- uio_out[2:0]: Head position (counts 0→7)

Test Loop Mode (Auto-restart):

Test Wrap Mode (Endless tape):

Test Custom STT:

Reset: ui_in = 10000000 (manual mode, bit 7=1)
Write 8 STT entries:
- Example: ui_in = 10000011 writes 0011 (S0,1,R) to address 0
- Increment address bits [6:4] for each entry
Exit config: ui_in = 00000000
Set tape: ui_in = 10101010
Next clock: Set head/state: ui_in = 00000011 (state 0, position 3)
Run: ui_in = 01100000 (Bank 3, no wrap/loop)

Test Output Swap:

For Tape Visualization:

For Status Display:

For Manual Control:

#	Input	Output	Bidirectional
0	IN0_HEAD_DECODE	TP_ST_0	ST_TP_0
1	IN1_TAPE_INIT	TP_ST_1	ST_TP_1
2	IN2_OUTPUT_SWAP	TP_ST_2	ST_TP_2
3	IN3_WRAP_EN	TP_ST_3	ST_TP_3
4	IN4_LOOP_EN	TP_ST_4	ST_TP_4
5	IN5_BANK_SEL0	TP_ST_5	ST_TP_5
6	IN6_BANK_SEL1	TP_ST_6	ST_TP_6
7	IN7_CUSTOM_AUTO	TP_ST_7	ST_TP_7

683 Tiny Turing Machine