Z80 Instruction Set

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Reference

Instruction Opcode Time S Z X H Y P N C Effect
adc a,R 10001rrr 4 + + + + + V 0 + a += R + cf
adc a,J 11i11101 1000110b 8 + + + + + V 0 + a += J + cf
adc a,N 11001110 nnnnnnnn 7 + + + + + V 0 + a += N + cf
adc a,(hl) 10001110 7 + + + + + V 0 + a += (hl) + cf
adc a,(I+D) 11i11101 10001110 dddddddd 19 + + + + + V 0 + a += (I+D) + cf
adc hl,Q 11101101 01qq1010 15 + + + + + V 0 + hl += Q + cf
add a,R 10000rrr 4 + + + + + V 0 + a += R
add a,J 11i11101 1000010b 8 + + + + + V 0 + a += J
add a,N 11000110 nnnnnnnn 7 + + + + + V 0 + a += N
add a,(hl) 10000110 7 + + + + + V 0 + a += (hl)
add a,(I+D) 11i11101 10000110 dddddddd 19 + + + + + V 0 + a += (I+D)
add hl,Q 00qq1001 11 - - + + + - 0 + hl += Q
add I,Q 11i11101 00qq1001 15 - - + + + - 0 + I += Q
and R 10100rrr 4 + + + 1 + P 0 0 a := a AND R
and J 11i11101 1010010b 8 + + + 1 + P 0 0 a := a AND J
and N 11100110 nnnnnnnn 7 + + + 1 + P 0 0 a := a AND N
and (hl) 10100110 7 + + + 1 + P 0 0 a := a AND (hl)
and (I+D) 11i11101 10100110 dddddddd 19 + + + 1 + P 0 0 a := a AND (I+D)
bit B,R 11001011 01bbbrrr 8 + + + 1 + P 0 - tmp := R AND [1 << B]
bit B,(hl) 11001011 01bbb110 12 + + X 1 X P 0 - tmp := (hl) AND [1 << B],
xf := memptr.13, yf := memptr.11
bit B,(I+D) 11i11101 11001011 dddddddd 01bbb*** 20 + + X 1 X P 0 - tmp := (I+D) AND [1 << B],
xf := [I+D].13, yf := [I+D].11
call A 11001101 alalalal ahahahah 17 - - - - - - - - sp -= 2, (sp) := pc, pc := A
call C,A 11ccc100 alalalal ahahahah 17/10 - - - - - - - - if C then sp -= 2, (sp) := pc, pc := A
ccf 00111111 4 - - A X A - 0 X hf := cf, cf := ~cf
cp R 10111rrr 4 + + X + X V 1 + tmp := a - R, xf := R.5, yf = R.3
cp J 11i11101 1011110b 8 + + X + X V 1 + tmp := a - J, xf := J.5, yf = J.3
cp N 11111110 nnnnnnnn 7 + + X + X V 1 + tmp := a - N, xf := N.5, yf = N.3
cp (hl) 10111110 7 + + X + X V 1 + tmp := a - (hl), xf := (hl).5, yf = (hl).3
cp (I+D) 11i11101 10111110 dddddddd 19 + + X + X V 1 + tmp := a - (I+D), xf := (I+D).5, yf = (I+D).3
cpd 11101101 10101001 16 + + X + X C 1 - tmp := a - (hl) => flags, bc -= 1, hl -= 1,
xf := [tmp - hf].1, yf = [tmp - hf].3
cpdr 11101101 10111001 21/16 + + X + X C 1 - cpd, if bc <> 0 and nz then pc -= 2
cpi 11101101 10100001 16 + + X + X C 1 - tmp := a - (hl) => flags, bc -= 1, hl += 1,
xf := [tmp - hf].1, yf = [tmp - hf].3
cpir 11101101 10110001 21/16 + + X + X C 1 - cpi, if bc <> 0 and nz then pc -= 2
cpl 00101111 4 - - + 1 + - 1 - a := ~a
daa 00100111 4 + + + X + P - X tmp := a,
if nf then
 if hf or [a AND 0x0f > 9] then tmp -= 0x06
 if cf or [a > 0x99] then tmp -= 0x60
else
 if hf or [a AND 0x0f > 9] then tmp += 0x06
 if cf or [a > 0x99] then tmp += 0x60
endif,
tmp => flags, cf := cf OR [a > 0x99],
hf := a.4 XOR tmp.4, a := tmp
dec R 00rrr101 4 + + + + + V 1 - R -= 1
dec J 11i11101 0010b101 8 + + + + + V 1 - J -= 1
dec (hl) 00110101 11 + + + + + V 1 - (hl) -= 1
dec (I+D) 11i11101 00110101 dddddddd 19 + + + + + V 1 - (I+D) -= 1
dec Q 00qq1011 6 - - - - - - - - Q -= 1
dec I 11i11101 00101011 10 - - - - - - - - I -= 1
di 11110011 4 - - - - - - - - iff1 := 0, iff2 := 0
djnz E 00010000 dddddddd 13/8 - - - - - - - - b -= 1, if b <> 0 then pc := E
ei 11111011 4 - - - - - - - - iff1 := 1, iff2 := 1 after the next instruction
ex (sp),hl 11100011 19 - - - - - - - - (sp) <=> hl
ex (sp),I 11i11101 11100011 23 - - - - - - - - (sp) <=> I
ex af,af' 00001000 4 X X X X X X X X af <=> af'
ex de,hl 11101011 4 - - - - - - - - de <=> hl
exx 11011001 4 - - - - - - - - bc, de, hl <=> bc', de', hl'
halt 01110110 4 - - - - - - - - wait for interrupt
im 0 11101101 01*0*110 8 - - - - - - - - mode 0: execute instruction on bus
im 1 11101101 01*10110 8 - - - - - - - - mode 1: execute rst $38
im 2 11101101 01*11110 8 - - - - - - - - mode 2: call (i * 256 + byte on bus)
in a,(N) 11011011 nnnnnnnn 11 - - - - - - - - a := ((N))
in R,(c) 11101101 01rrr000 12 + + + 0 + P 0 - R := ((c))
in f,(c) 11101101 01110000 12 + + + 0 + P 0 - tmp := ((c))
inc R 00rrr100 4 + + + + + V 0 - R += 1
inc J 11i11101 0010b100 8 + + + + + V 0 - J += 1
inc (hl) 00110100 11 + + + + + V 0 - (hl) += 1
inc (I+D) 11i11101 00110100 dddddddd 23 + + + + + V 0 - (I+D) += 1
inc Q 00qq0011 6 - - - - - - - - Q += 1
inc I 11i11101 00100011 10 - - - - - - - - I += 1
ind 11101101 10101010 16 + + + X + X X X tmp := ((c)), (hl) := tmp, hl -= 1,
b -= 1 => flags, nf := tmp.7,
tmp2 = tmp + [[c - 1] AND 0xff],
pf := parity of [[tmp2 AND 0x07] XOR b],
hf := cf := tmp2 > 255
indr 11101101 10111010 21/16 + + + X + X X X ind, if b <> 0 then pc -= 2
ini 11101101 10100010 16 + + + X + X X X tmp := ((c)), (hl) := tmp, hl += 1,
b -= 1 => flags, nf := tmp.7,
tmp2 := tmp + [[c + 1] AND 0xff],
pf := parity of [[tmp2 AND 0x07] XOR b],
hf := cf := tmp2 > 255
inir 11101101 10110010 21/16 + + + X + X X X ini, if b <> 0 then pc -= 2
jp A 11000011 alalalal ahahahah 10 - - - - - - - - pc := A
jp (hl) 11101001 4 - - - - - - - - pc := hl
jp (I) 11i11101 11101001 8 - - - - - - - - pc := I
jp C,A 11ccc010 alalalal ahahahah 10 - - - - - - - - if C then pc := A
jr E 00011000 dddddddd 12 - - - - - - - - pc := E
jr nz,E 00100000 dddddddd 12/7 - - - - - - - - if nz then pc := E
jr z,E 00101000 dddddddd 12/7 - - - - - - - - if zf then pc := E
jr nc,E 00110000 dddddddd 12/7 - - - - - - - - if nc then pc := E
jr c,E 00111000 dddddddd 12/7 - - - - - - - - if cf then pc := E
ld R1,R2 01rrrsss 4 - - - - - - - - R1 := R2
ld R,J 11i11101 01rrr10b 8 - - - - - - - - R := J
ld J,R 11i11101 0110brrr 8 - - - - - - - - J := R
ld ixh,ixl 11011101 01100101 8 - - - - - - - - ixh := ixl
ld ixl,ixh 11011101 01101100 8 - - - - - - - - ixl := ixh
ld iyh,iyl 11111101 01100101 8 - - - - - - - - iyh := iyl
ld iyl,iyh 11111101 01101100 8 - - - - - - - - iyl := iyh
ld R,N 00rrr110 nnnnnnnn 7 - - - - - - - - R := N
ld R,(hl) 01rrr110 7 - - - - - - - - R := (hl)
ld R,(I+D) 11i11101 01rrr110 dddddddd 19 - - - - - - - - R := (I+D)
ld (hl),R 01110rrr 7 - - - - - - - - (hl) := R
ld (hl),N 00110110 nnnnnnnn 10 - - - - - - - - (hl) := N
ld (I+D),R 11i11101 01110rrr dddddddd 19 - - - - - - - - (I+D) := R
ld (I+D),N 11i11101 00110110 dddddddd nnnnnnnn 19 - - - - - - - - (I+D) := N
ld a,(bc) 00001010 7 - - - - - - - - a := (bc)
ld a,(de) 00011010 7 - - - - - - - - a := (de)
ld a,(A) 00111010 alalalal ahahahah 13 - - - - - - - - a := (A)
ld (bc),a 00000010 7 - - - - - - - - (bc) := a
ld (de),a 00010010 7 - - - - - - - - (de) := a
ld (A),a 00110010 alalalal ahahahah 13 - - - - - - - - (A) := a
ld i,a 11101101 01000111 9 - - - - - - - - i := a
ld r,a 11101101 01001111 9 - - - - - - - - r := a
ld a,i 11101101 01010111 9 + + + 0 + X 0 - a := i, pf := iff2
ld a,r 11101101 01011111 9 + + + 0 + X 0 - a := r, pf := iff2
ld Q,A 00qq0001 alalalal ahahahah 10 - - - - - - - - Q := A
ld I,A 11i11101 00100001 alalalal ahahahah 14 - - - - - - - - I := A
ld Q,(A) 11101101 01qq1011 alalalal ahahahah 20 - - - - - - - - Q := (A) [ld hl,(A) has a faster non-prefixed duplicate, see below.]
ld hl,(A) 00101010 alalalal ahahahah 16 - - - - - - - - hl := (A)
ld I,(A) 11i11101 00101010 alalalal ahahahah 20 - - - - - - - - I := (A)
ld (A),Q 11101101 01qq0011 alalalal ahahahah 20 - - - - - - - - (A) := Q [ld (A),hl has a faster non-prefixed duplicate, see below.]
ld (A),hl 00100010 alalalal ahahahah 16 - - - - - - - - (A) := hl
ld (A),I 11i11101 00100010 alalalal ahahahah 20 - - - - - - - - (A) := I
ld sp,hl 11111001 6 - - - - - - - - sp := hl
ld sp,I 11i11101 11111001 10 - - - - - - - - sp := I
ldd 11101101 10101000 16 - - X 0 X C 0 - tmp := (hl), (de) := tmp, de -= 1, hl -= 1,
bc -= 1, xf := [tmp + a].1, yf = [tmp + a].3
lddr 11101101 10111000 21/16 - - X 0 X C 0 - ldd, if bc <> 0 then pc -= 2
ldi 11101101 10100000 16 - - X 0 X C 0 - tmp := (hl), (de) := tmp, de += 1, hl += 1,
bc -= 1, xf := [tmp + a].1, yf = [tmp + a].3
ldir 11101101 10110000 21/16 - - X 0 X C 0 - ldi, if bc <> 0 then pc -= 2
neg 11101101 01***100 8 + + + + + V 1 + a := 0 - a
nop 00000000 4 - - - - - - - - nothing
or R 10110rrr 4 + + + 0 + P 0 0 a := a OR R
or J 11i11101 1011010b 8 + + + 0 + P 0 0 a := a OR J
or N 11110110 nnnnnnnn 7 + + + 0 + P 0 0 a := a OR N
or (hl) 10110110 7 + + + 0 + P 0 0 a := a OR (hl)
or (I+D) 11i11101 10110110 dddddddd 19 + + + 0 + P 0 0 a := a OR (I+D)
out (N),a 11010011 nnnnnnnn 11 - - - - - - - - ((N)) := a
out (c),R 11101101 01rrr001 12 - - - - - - - - ((c)) := R
out (c),0 11101101 01110001 12 - - - - - - - - ((c)) := ? (seems to vary with CPU)
outd 11101101 10101011 16 + + + X + X X X tmp := (hl), ((c)) := tmp, hl -= 1,
b -= 1 => flags, nf := tmp.7, tmp2 = tmp + l,
pf := parity of [[tmp2 AND 0x07] XOR b],
hf := cf := tmp2 > 255
otdr 11101101 10111011 21/16 + + + X + X X X outd, if b <> 0 then pc -= 2
outi 11101101 10100011 16 + + + X + X X X tmp := (hl), ((c)) := tmp, hl += 1,
b -= 1 => flags, nf := tmp.7, tmp2 = tmp + l,
pf := parity of [[tmp2 AND 0x07] XOR b],
hf := cf := tmp2 > 255
otir 11101101 10110011 21/16 + + + X + X X X outi, if b <> 0 then pc -= 2
pop P 11pp0001 10 - - - - - - - - P := (sp), sp += 2
pop I 11i11101 11100001 14 - - - - - - - - I := (sp), sp += 2
push P 11pp0101 11 - - - - - - - - sp -= 2, (sp) := P
push I 11i11101 11100101 15 - - - - - - - - sp -= 2, (sp) := I
res B,R 11001011 10bbbrrr 8 - - - - - - - - R := R AND ~[1 << B]
res B,(hl) 11001011 10bbb110 15 - - - - - - - - (hl) := (hl) AND ~[1 << B]
res B,(I+D) 11i11101 11001011 dddddddd 10bbb110 23 - - - - - - - - (I+D) := (I+D) AND ~[1 << B]
res B,(I+D)->R 11i11101 11001011 dddddddd 10bbbrrr 23 - - - - - - - - (I+D) := R := (I+D) AND ~[1 << B]
ret 11001001 10 - - - - - - - - pc := (sp), sp += 2
ret C 11ccc000 11/5 - - - - - - - - if C then pc := (sp), sp += 2
reti 11101101 01**1101 14 - - - - - - - - pc := (sp), sp += 2, iff1 := iff2
retn 11101101 01**0101 14 - - - - - - - - pc := (sp), sp += 2, iff1 := iff2
rla 00010111 4 - - + 0 + - 0 X ocf := cf, cf := a.7, a := [a << 1] + ocf
rl R 11001011 00010rrr 8 + + + 0 + P 0 X ocf := cf, cf := R.7, R := [R << 1] + ocf
rl (hl) 11001011 00010110 15 + + + 0 + P 0 X ocf := cf, cf := (hl).7, (hl) := [(hl) << 1] + ocf
rl (I+D) 11i11101 11001011 dddddddd 00010110 23 + + + 0 + P 0 X ocf := cf, cf := (I+D).7,
(I+D) := [(I+D) << 1] + ocf
rl (I+D)->R 11i11101 11001011 dddddddd 00010rrr 23 + + + 0 + P 0 X ocf := cf, cf := (I+D).7,
(I+D) := R := [(I+D) << 1] + ocf
rlca 00000111 4 - - + 0 + - 0 X cf := a.7, a := [a << 1] + cf
rlc R 11001011 00000rrr 8 + + + 0 + P 0 X cf := R.7, R := [R << 1] + cf
rlc (hl) 11001011 00000110 15 + + + 0 + P 0 X cf := (hl).7, (hl) := [(hl) << 1] + cf
rlc (I+D) 11i11101 11001011 dddddddd 00000110 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := [(I+D) << 1] + cf
rlc (I+D)->R 11i11101 11001011 dddddddd 00000rrr 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := R := [(I+D) << 1] + cf
rld 11101101 01101111 18 + + + 0 + P 0 - tmp := [(hl) << 4] + [a AND 0x0f], (hl) := tmp,
a := [a AND 0xf0] + [tmp >> 8] => flags
rra 00011111 4 - - + 0 + - 0 X ocf := cf, cf := a.0, a := [a >> 1] + [ocf << 7]
rr R 11001011 00011rrr 8 + + + 0 + P 0 X ocf := cf, cf := R.0, R := [R >> 1] + [ocf << 7]
rr (hl) 11001011 00011110 15 + + + 0 + P 0 X ocf := cf, cf := (hl).0,
(hl) := [(hl) >> 1] + [ocf << 7]
rr (I+D) 11i11101 11001011 dddddddd 00011110 23 + + + 0 + P 0 X ocf := cf, cf := (I+D).0,
(I+D) := [(I+D) >> 1] + [ocf << 7]
rr (I+D)->R 11i11101 11001011 dddddddd 00011rrr 23 + + + 0 + P 0 X ocf := cf, cf := (I+D).0,
(I+D) := R := [(I+D) >> 1] + [ocf << 7]
rrca 00001111 4 - - + 0 + - 0 X cf := a.0, a := [a >> 1] + [cf << 7]
rrc R 11001011 00001rrr 8 + + + 0 + P 0 X cf := R.0, R := [R >> 1] + [cf << 7]
rrc (hl) 11001011 00001110 15 + + + 0 + P 0 X cf := (hl).0, (hl) := [(hl) >> 1] + [cf << 7]
rrc (I+D) 11i11101 11001011 dddddddd 00001110 23 + + + 0 + P 0 X cf := (I+D).0, (I+D) := [(I+D) >> 1] + [cf << 7]
rrc (I+D)->R 11i11101 11001011 dddddddd 00001rrr 23 + + + 0 + P 0 X cf := (I+D).0,
(I+D) := R := [(I+D) >> 1] + [cf << 7]
rrd 11101101 01100111 18 + + + 0 + P 0 - tmp := (hl),
(hl) := [tmp >> 4] + [[a AND 0x0f] << 4],
a := [a AND 0xf0] + [tmp AND 0x0f] => flags
rst S 11sss111 11 - - - - - - - - sp -= 2, (sp) := pc, pc := S
sbc a,R 10011rrr 4 + + + + + V 1 + a -= R + cf
sbc a,J 11i11101 1001110b 8 + + + + + V 1 + a -= J + cf
sbc a,N 11011110 nnnnnnnn 7 + + + + + V 1 + a -= N + cf
sbc a,(hl) 10011110 7 + + + + + V 1 + a -= (hl) + cf
sbc a,(I+D) 11i11101 10011110 dddddddd 19 + + + + + V 1 + a -= (I+D) + cf
sbc hl,Q 11101101 01qq0010 15 + + + + + V 1 + hl -= Q + cf
scf 00110111 4 - - A 0 A - 0 1 nothing else
set B,R 11001011 11bbbrrr 8 - - - - - - - - R := R OR [1 << B]
set B,(hl) 11001011 11bbb110 15 - - - - - - - - (hl) := (hl) OR [1 << B]
set B,(I+D) 11i11101 11001011 dddddddd 11bbb110 23 - - - - - - - - (I+D) := (I+D) OR [1 << B]
set B,(I+D)->R 11i11101 11001011 dddddddd 11bbbrrr 23 - - - - - - - - (I+D) := R := (I+D) OR [1 << B]
sla R 11001011 00100rrr 8 + + + 0 + P 0 X cf := R.7, R := R << 1
sla (hl) 11001011 00100110 15 + + + 0 + P 0 X cf := (hl).7, (hl) := (hl) << 1
sla (I+D) 11i11101 11001011 dddddddd 00100110 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := (I+D) << 1
sla (I+D)->R 11i11101 11001011 dddddddd 00100rrr 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := R := (I+D) << 1
sra R 11001011 00101rrr 8 + + + 0 + P 0 X cf := R.0, R := R >> 1, R.7 := R.6
sra (hl) 11001011 00101110 15 + + + 0 + P 0 X cf := (hl).0, (hl) := (hl) >> 1, (hl).7 := (hl).6
sra (I+D) 11i11101 11001011 dddddddd 00101110 23 + + + 0 + P 0 X cf := (I+D).0,
(I+D) := (I+D) >> 1, (I+D).7 := (I+D).6
sra (I+D)->R 11i11101 11001011 dddddddd 00101rrr 23 + + + 0 + P 0 X cf := (I+D).0,
tmp := (I+D) >> 1, tmp.7 := tmp.6
(I+D) := R := tmp
sll R 11001011 00110rrr 8 + + + 0 + P 0 X cf := R.7, R := [R << 1] + 1
sll (hl) 11001011 00110110 15 + + + 0 + P 0 X cf := (hl).7, (hl) := [(hl) << 1] + 1
sll (I+D) 11i11101 11001011 dddddddd 00110110 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := [(I+D) << 1] + 1
sll (I+D)->R 11i11101 11001011 dddddddd 00110rrr 23 + + + 0 + P 0 X cf := (I+D).7, (I+D) := R := [(I+D) << 1] + 1
srl R 11001011 00111rrr 8 0 + + 0 + P 0 X cf := R.0, R := R >> 1
srl (hl) 11001011 00111110 15 0 + + 0 + P 0 X cf := (hl).0, (hl) := (hl) >> 1
srl (I+D) 11i11101 11001011 dddddddd 00111110 23 0 + + 0 + P 0 X cf := (I+D).0, (I+D) := (I+D) >> 1
srl (I+D)->R 11i11101 11001011 dddddddd 00111rrr 23 0 + + 0 + P 0 X cf := (I+D).0, (I+D) := R := (I+D) >> 1
sub R 10010rrr 4 + + + + + V 1 + a -= R
sub J 11i11101 1001010b 8 + + + + + V 1 + a -= J
sub N 11010110 nnnnnnnn 7 + + + + + V 1 + a -= N
sub (hl) 10010110 7 + + + + + V 1 + a -= (hl)
sub (I+D) 11i11101 10010110 dddddddd 19 + + + + + V 1 + a -= (I+D)
xor R 10101rrr 4 + + + 0 + P 0 0 a := a XOR R
xor J 11i11101 1010110b 8 + + + 0 + P 0 0 a := a XOR J
xor N 11101110 nnnnnnnn 7 + + + 0 + P 0 0 a := a XOR N
xor (hl) 10101110 7 + + + 0 + P 0 0 a := a XOR (hl)
xor (I+D) 11i11101 10101110 dddddddd 19 + + + 0 + P 0 0 a := a XOR (I+D)

Legend

Notation Meaning Respective opcode bits
A 16-bit address or immediate alalalal ahahahah
B Bit number: 0..7 bbb = 000..111
C Condition: nz, z, nc, c, po, pe, p, m ccc = 000, 001, 010, 011, 100, 101, 110, 111
D 8-bit signed relative offset dddddddd
E 16-bit relative address dddddddd (E minus address of next instruction)
I Index register: ix, iy i = 0, 1
J Half index register: ixh, ixl, iyh, iyl (i, b) = (0, 0), (0, 1), (1, 0), (1, 1)
N 8-bit immediate nnnnnnnn
P 16-bit register pair: bc, de, hl, af pp = 00, 01, 10, 11
Q 16-bit register: bc, de, hl/ix/iy, sp qq = 00, 01, 10, 11
R 8-bit general purpose register: a, b, c, d, e, h, l rrr (or sss) = 111, 000, 001, 010, 011, 100, 101
S Restart address: 0x00, 0x08,..., 0x38 sss = 000, 001,..., 111

Flags

  • - = no change
  • + = change by definition (if noted, by the operation marked with '=> flags', otherwise by the only non-single-bit operation):
    • S = sign, bit 7 of the result byte (accumulator or high byte for 16-bit operations)
    • Z = zero, set if the result is zero (8 or 16-bit value)
    • X = undocumented, bit 5 of the result byte
    • H = half-carry, the carry (theoretical bit 4) of the low nibble of the result byte
    • Y = undocumented, bit 3 of the result byte
    • P = parity (set if the result byte has an even number of bits set) or overflow (set when crossing the boundary of the signed range); always specified
    • N = negative, set if the previous operation was a subtraction; always specified
    • C = carry, the theoretical bit 8 of the result byte
  • 0 = always reset
  • 1 = always set
  • X = change described under Effect
  • P = parity (only for the parity flag)
  • V = overflow (only for the parity flag)
  • A = OR with the respective bit of the accumulator
  • C = set if the counter (bc) is nonzero after decrementing

Miscellaneous

  • () = indirection
  • (()) = I/O port
  • [] = operator precedence (to avoid confusion with indirection)
  • E.B = the Bth bit of the value of expression E
  • * = any bit value (0 or 1)
  • memptr = an internal 16-bit register connected to 16-bit operations
  • tmp, tmp2 = temporary storage whose value is thrown away after each instruction

English Language Explanations

Data Movement

EX Three possible arguments:

EX DE, HL Swaps H with D and L with E

EX AF, AF' Swaps AF with its shadow

EX (SP), HL Swaps (SP) with L and (SP+1) with H. Index registers are also valid


EXX Swap BC, DE and HL with their shadows


LD Four main arguments:

LD reg, # Sets the eight or 16 bit contents of reg to #

LD reg2, reg1 Copies the contents of 8 bit reg1 to reg2

LD (imm16), reg Copies the value of 8 or 16 bit reg to 16 bit memory address imm16. Programmers should remember that 16 bit values are stored little-endian.

LD reg, (imm16) Does the opposite of LD (imm16), reg


LDIR Copies a byte from (HL) to (DE), increments DE and HL, then decrements BC. The instruction is repeated if BC is not 0. Interrupts are allowed to trigger while this instruction is running.


PUSH Used as PUSH reg16 where reg16 is a register pair or index register. Decrements SP, copies regMSB to (SP), decrements SP again, then copies regLSB to (SP).


POP Same syntax as PUSH. Copies (SP) to regLSB, increments SP, copies (SP) to regMSB, then increments SP again. The word based at the starting value of SP is zeroed.


Control

JP JP imm16 Imm16 is copied to PC, causing execution to jump there. Can also be conditional with Z, NZ, C, NC, PO, PE, P, or M as additional arguments such as JP Z, imm16. (HL) may be substituted for imm16 to have the current value of HL copied to PC


JR JR imm8 The signed 8 bit value imm8 is added to PC, allowing a jump within 128 bytes of the instruction. May also be conditional, but only with Z, NZ, C, and NC arguments.


CALL CALL imm16 The current value of PC+3 is PUSHed, then imm16 is loaded into PC. May be conditional with the same syntax and arguments as JP, although (HL) is not valid.


RET RET The top stack value is POPed into PC. It may be conditional with the same arguments and syntax as JP. This is usually used to return from a CALL instruction.


RST RST imm8 PC+1 is PUSHed and PC is loaded with 00imm8. This opcode is only 1 byte, so it is an alternative to CALLing routines that are mapped into the beginning of memory. However, it may only be used for the following values of imm8: 00h, 08h, 18h, 20h, 28h, 30h, and 38h. Imm8 must also be in -h suffix format.

DJNZ DJNZ imm8 B is decremented and if is 0, the rest of the instruction is skipped. Otherwise, the signed 8 bit value imm8 is added to PC. This instruction is usually used like a For( loop in BASIC.


NOP NOP As the name implies, it is "no operation". The CPU does nothing for four clock cycles.


Care of

  • Reference table thanks to CoBB
  • English language reference thanks to Taricorp
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