# vim: noet ts=4 sw=4 ft=yaml :

[metadata]
name: z80
bits: 8
endianness: little
signedness: twos-complement
cache: none
pipeline: none

[attributes]
imm[8]: cycles +3
imm[16]: cycles +6
*: cycles +3

[registers]
AF: 16; special
	A: 8; accumulator
	F: 8; flags, offset 8;; flag
		_C:  1
		_N:  1; offset 1
		_PV: 1; offset 2
		_3:  1; offset 3, undocumented
		_H:  1; offset 4
		_5:  1; offset 5, undocumented
		_Z:  1; offset 6
		_S:  1; offset 7
BC: 16
	B: 8
	C: 8; offset=8
DE: 16
	D: 8
	E: 8; offset=8
HL: 16
	H: 8
	L: 8; offset=8
SP: 16; stack
PC: 16; program
# Index registers
IX: 16
	IXH: 8; undocumented
	IXL: 8; undocumented, offset 8
IY: bits=16
	IYH: 8; undocumented
	IYL: 8; undocumented, offset 8
# Interrupt and memory refresh register
I: 8; special, volatile
R: 8; special, volatile
# Shadow registers, can be swapped with the main set via ex/exx
"AF'": 16; special
"BC'": 16; special
"DE'": 16; special
"HL'": 16; special

[macros]
flags_zc: ;; imply[conditional]
	NZ: 00; imply[uses _Z]
	Z: 01; imply[uses _Z]
	NC: 10; imply[uses _C]
	C: 11; imply[uses _C]
flags: ;; imply[conditional]
	NZ: 000; imply[uses _Z]
	Z: 001; imply[uses _Z]
	NC: 010; imply[uses _C]
	C: 011; imply[uses _C]
	PO: 100; imply[uses _PV]
	PE: 101; imply[uses _PV]
	P: 110; imply[uses _S]
	M: 111; imply[uses _S]
reg_8:
	A: 111; imply[uses A]
	B: 000; imply[uses B]
	C: 001; imply[uses C]
	D: 010; imply[uses D]
	E: 011; imply[uses E]
	H: 100; imply[uses H]
	L: 101; imply[uses L]
	*HL: 110; imply[uses HL]
reg_BCDE:
	BC: 0; imply[uses BC]
	DE: 1; imply[uses DE]
reg_IR:
	I: 0; imply[uses I]
	R: 1; imply[uses R]
reg_BCDEHLSP:
	BC: 00; imply[uses BC]
	DE: 01; imply[uses DE]
	HL: 10; imply[uses HL]
	SP: 11; imply[uses SP]
reg_BCDEHLAF:
	BC: 00; imply[uses BC]
	DE: 01; imply[uses DE]
	HL: 10; imply[uses HL]
	AF: 11; imply[uses AF]
reg_BCDEIXSP:
	BC: 00; imply[uses BC]
	DE: 01; imply[uses DE]
	IX: 10; imply[uses IX]
	SP: 11; imply[uses SP]
reg_BCDEIYSP:
	BC: 00; imply[uses BC]
	DE: 01; imply[uses DE]
	IY: 10; imply[uses IY]
	SP: 11; imply[uses SP]
reg_index:
	IX: 11011101; imply[uses IX, cycles +4]
	IY: 11111101; imply[uses IY, cycles +4]
# on z80, you can offset indirect references to certain registers by an
# immediate value
reg_index_ind:
	*(reg_index @imm[8; signed, name offset]); imply[cycles +8]
# on z80, you can access the low and high octets of index registers through
# some undocumented instructions
reg_ihl: ;; imply[undocumented]
	IXH: 100; define[ireg=11011101], imply[uses IXH]
	IXL: 101; define[ireg=11011101], imply[uses IXL]
	IYH: 100; define[ireg=11111101], imply[uses IYH]
	IYL: 101; define[ireg=11111101], imply[uses IYL]

[instructions]
.load:
	ld: ;; load[dest, source], cycles +4
		@reg_8, @reg_8: 01 $1 $2
		@reg_8, @imm[8]: 00 $1 110 $2

		%A, *@reg_BCDE: 000 $2 1010
		%A, *@imm[16]: 000 $2 1010
		*@reg_BCDE, %A: 000 $1 0010
		*@imm[16], %A: 00110010 $1

		%A, @reg_IR: 11101101 0101 $2 111; cycles 9, flags[_S,_Z,_H:0,_N:0,_PV:?]
		@reg_IR, %A: 11101101 0100 $1 111; cycles 9

		@reg_BCDEHLSP, @imm[16]: 00 $1 0001 $2

		%HL, *@imm[16]: 00101010 $2; cycles 16
		@reg_BCDEHLSP, *@imm[16]: 11101101 01 $1 1011 $2; cycles 20
		*@imm[16], %HL: 00100010 $1; cycles 16
		*@imm[16], @reg_BCDEHLSP: 11101101 01 $2 0011 $1; cycles 20

		%SP, %HL: 1111001; cycles +2
.copy:
	ldd: 11101101 10101000; uses[HL, DE], \
		affects[HL[--], DE[--], BC[--]], \
		flags[_H:0,_N:0,_PV:[BC == 0]], cycles 16
	lddr: 11101101 10111000; uses[HL, DE, BC], \
		affects[HL[-BC], DE[-BC], BC[0]], \
		flags[_H:0,_N:0,_PV:0], cycles[16 + BC * 5]
	ldi: 11101101 10100000; uses[HL, DE], \
		affects[HL[++], DE[++], BC[--]], \
		flags[_H:0,_N:0,_PV:[BC == 0]], cycles 16
	ldir: 11101101 10110000; uses[HL, DE, BC], \
		affects[HL[+BC], DE[+BC], BC[0]], \
		flags[_H:0,_N:0,_PV:0], cycles[16 + BC * 5]
.index:
	ld: ;; load[dest, source], cycles +4
		@reg_index, @imm[16]: $1 00100001 $2

		@reg_8, @reg_index_ind: $2 01 $1 110 $offset
		@reg_index_ind, @reg_8: $1 01110 $2 $offset
		@reg_index_ind, @imm[8]: $1 00110110 $offset $2

		@reg_index, *@imm[16]: $1 00101010 $2; cycles 20
		*@imm[16], @reg_index: $2 00100010 $1; cycles 20

		%SP, @reg_index: $2 1111001; cycles +2, uses SP

		@reg_ihl, @reg_8: $ireg 01 $1 $2
		@reg_ihl, @imm[8]: $ireg 00 $1 110 $2
.z80:
	ex: ;; reversible
		%DE, %HL: 11101011; cycles 4
		%AF, %"AF'": 00001000; cycles 4
		*%SP, %HL: 11100011; cycles 19
		*%SP, @reg_index: $1 11100011; cycles 23
	exx: 11011001; cycles 4