stacard vm reference

Features

• Stack-based
• 256 12-bit words memory

Instruction set

Experimental instructions

Assembler

Pseudoblock

Pseudoblock is defined by single { and } on lines. Inside pseudoblock you can use =begin and =end labels that represent nearest braces

Example

ld @zero
st @counter
{
    ld @limit
    ld @counter
    sub
    jz =end
    jlz =end    ; leave pseudoblock if counter >= limit
    ...
    ld @counter
    inc
    st @counter ; increment counter
    jmp =begin  ; next iteration
}

Memory address

Numeric address

ld 102
jmp 50

Label

Defining label

var:
    data 100
label1:
    brk

Referencing label

ld @var
jmp @label1

Pseudoblock

jmp =begin
jmp =end

Initializing memory locations

Numeric data

var1:
    data 128

String

str1:
    string Test

Pointer

ptr1:
    data @var1

Example program

	ld @strptr        ; load string address
	{
		dup
		jsr @iload    ; call subroutine for indirect load
		jz =end       ; if zero jump outside of brackets block (=end)
		printch
		drop
		inc
		jmp =begin    ; jump to block start
	}
	drop              ; clean stack
	drop
	brk
str:
	string Hello
	data 32
	string world!
	data 0
strptr:
	data @str
load_op:
	data 256
iload:
	swap
	ld @load_op
	add               ; making ld instruction with passed address
	st @iload2        ; indirect loading via self-modifying code
iload2:
	brk
	swap
	ji