gistfile1.txt

AREIA-1
------------

16 registers, 16 bits each,
        0 = always 0
        15 = SP

Memory is treated as little-endian.
Opcode byte: oooooott (o - opcode, t - type of opcode)
l is .b or .w
Opcode formats:
	OP0     00oooo00
	OP1.1   01oooo0l xxxxyyyy (@x, @y)
	OP1.2   01oooo1l xxxxyyyy iiiiiiii [iiiiiiii] (@x, #i, @y is used as a destination reg when sane, like @x + #i -> @y)
	OP2.1   11oooo00 xxxxbbbb aaaaaaaa aaaaaaaa (jmp $baaaa + @x)
	OP2.2   11oooo01 aaaaaaaa aaaaaaaa (jmp $Saaaa)
	OP2.3   11oooo1l aaaaaaaa [aaaaaaaa] - RELATIVE BRANCHES
	OP3.1   10ooaa00 xxxxyyyy (ld @x, $Syyyy)
	OP3.2.  10ooaa01 xxxxbbbb aaaaaaaa aaaaaaaa (ld @x, $baaaa)
	OP3.3.  10ooaa10 xxxxyyyy aaaaaaaa aaaaaaaa (ld @x, $Saaaa + @y)
	OP3.4.  10ooaa11 xxxxyyyy zzzzaaaa (ld @x, $zyyyy + @a)

Addressing modes:
	0 - regular
	1 - indirect ( [@y])
	2 - stack (@y + SP)
	3 - indirect stack ([@y + SP[)
	
Opcodes:
	OP0     nop, ret, popf, pushf, cli, sei, hlt, ss0, ss1
	OP1     move, cmp, add, sub, xor, or, and, asl, asr, lsr, rol, ror, rcl, rcr
	OP2     all the jumps
	OP3     ld.b, st.b, ld.w, st.w 
	

Notes:
	move with @0 as destination is:
		for l=0, move.b SEGMENT, @y
		for l=1, move.b @y, SEGMENT


FLAGS:
    bit     description
---------------------------------------
    0       ZERO (CMP equality)
    1       CARRY (whether carrying a bit, for subtract follow Z80 impl.)
    2       OVERFLOW (add/sub/cmp: if signed overflow occurs; xor/and/or: sum of all bits over GF(2) (parity))
    3       SIGNED (whether >= 0x8000 or >= 0x80 for b)
    4       INTERRUPT (set to 1 to enable)
    5-15    Reserved.

OP2.3 1110oooo xxxxbbbb aaaaaaaa aaaaaaaa (jmp [$baaaa + @x] - indirect)

Change this to

OP2.3 1110oooo xxxxbbbb aaaaaaaa (jmp PC + @x + (signed)$baa)