Test3d

Low-tech computing for Minetest

Memory access

Memory access in this mod occurs over digilines, with the channel as the prefix plus the memory address, and the message as either the new value or 'get' to get it returned, so for example:

Prefix	Address	Value	Channel	Message
A	1	4	A1	4
Default	15	get	DefaultF	get

T400

The T400 is a 12-bit stack machine operating at 1Hz (due to ABMs only running once per second). It has a 16-word stack, 0 registers and a very simple instruction set.

Instructions

There are 8 instructions for the T400. Any values encountered by the processor that are not instructions are treated as data and pushed to the stack. While this does make both the code for the emulator and the code for the emulated computer simple, it has the downside that if you really do want the value 4095 you have to add two things together.

ins	function	mnemonic
4095	push program counter	ppc
4094	swap TOS	swp
4093	read memory from TOS	read
4092	write to memory from TOS	write
4091	add TOS	add
4090	suptract TOS	sub
4089	jump to TOS	jmp
4088	skip if TOS = zero	sez
4087	jump if TOS = zero	jez
4086	jump to subroutine, push pc to retstack	jsr
4085	return from subroutine, PC = top of retstack	ret
4084	duplicate TOS	dup
4083	drop TOS	drop

T410

The T410, is, in essence, the write instruction in a block. You put in an address and a value and it tries to write the value to that address.

T416

The T416 is a 16-word memory. It stores 16 ints and is accessed as described in the Memory access section.