SVM/SPEC.md

Features

• 4 16-bit Registers
• 254 8-bit Flag Registers
  • Start at end of memory from 0xFF00
  • See FLAGS.md
• 255 8-bit Ports
  • 0x00 console in/out
  • 0x01 tape in/out
  • 0x02-0x20 Reserved
  • Others Implementation Specific
• 255 Syscall routines
• Program Counter
• Call Stack 16 x 16-bit
• 64K x 8-bit Memory
• MSB / big-endian

ASM Parameters

Type	Symbol	Example/Use
Registers	R	A-D
Marker	:	:XYZ
Absolute Location	#	0-65535 | 0xFFFF

Location Parameter (@)

Code	ASM	Type	Values
0x0	P	Port	0-255 | 0xFF
0x1	R	Register	A-D
0x2	M	Memory	0-65535 | 0xFFFF
0x3	L	Immediate	0-65535 | 0xFFFF | 'a' | "a"
0x4	A	Address In Register	A-D

ASM Instructions

Hex	ASM	Parameters	Notes
Misc
0x00	NOP
Load/Save
0x10	LOAD	[R] [@]
0x11	SAVE	[R] [@]
0x12	LOADH	[R] [@]
0x13	LOADL	[R] [@]
0x14	SAVEH	[R] [@]
0x15	SAVEL	[R] [@]
Math
0x20	CLR	[R]
0x21	ADD	[R] [@]
0x22	SUB	[R] [@]
0x23	DIV	[R] [@]
0x24	MUL	[R] [@]
0x25	INC	[R]
0x26	DEC	[R]
Logic
0x30	NOT	[R]
0x31	AND	[R] [@]
0x32	OR	[R] [@]
0x33	XOR	[R] [@]
0x34	SHL	[R] [0-7]	Shift Left
0x35	SHR	[R] [0-7]	Shift Right
0x36	BTS	[R] [0-7]	Bit Set
0x37	BTC	[R] [0-7]	Bit Clear
Stack
0x40	CALL	[#|:]
0x41	RET
Program Flow
0x50	HALT
0x51	JMP	[#|:]
0x52	JZ	[R] [#|:]
0x53	JNZ	[R] [#|:]
0x54	JBS	[R] [0-7] [#|:]
0x55	JBC	[R] [0-7] [#|:]
System
0x60	SYS	[0-255]	Syscall, parameters depend on call

Assembler Only

ASM	Parameters	Notes
ORIGIN	[#]	Sets the Memory Address for the next instruction

Program Format

ORIGIN 0
:MARKERA    JMP :MARKERB    # This is a comment
:MARKERB    INC A
            JMP :MARKERA
[...ASM Instrictions...]
MEMORY
0x100 "string abcd"
100 0x00 00 00