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z80 conditional jump
cp hl z80
z80 ld
z80 clear carry flag
z80 flags
z80 clear zero flag
z80 and
z80 cp
The flags are set according to the result of the last instruction. The standard behaviour is: S - Sign flag: Set if the 2-complement value is negative (copy of MSB); Z - Zero flag: Set if the value is zero; F5 - undocumented flag: Copy of bit 5; H - Half Carry: Carry from bit 3 to bit 4; F3 - undocumented flag: Copy of bit 3; P/V - Parity
11 Jun 2010 Possible the most powerful instructions in the z80 arsenal, bitwise instructions allow you not only to change flags, but you can also modify any byte. set 0,a res 5,(hl). So, which one is the zeroth bit or fifth bit? The least significant bit (LSB, or 0th bit) is always the bit furthest right and the most significant bit
Z80 Assembly - Instructions: Working With Data. The notation op8 denotes either A, B, C, D, E, H, L, IXH, IXL, IYH, IYL, (HL), (IX+n), (IY+n) or a 8-bit immediate (constant). Arithmetic operations. This section includes all the instructions that perform basic mathematical operations. ADD. Syntax: add a,op8 (8 bits) or add reg16
Beyond addition and subtraction there are numerous other ways in which you can affect registers. They are called bitwise instruction because they work at the level of bits. AND is short for, erm, and and works by comparing each bit and setting the result bit to 1 if they are both 1. For example:.
n can be any integer from [0,7]. It must be defined on compile time. bit n,a bit n,b bit n,c bit n,d bit n,e bit n,h bit n,l bit n,(hl) bit n,(ix+n) bit n,(iy+n)
H: See instruction. Z: Set if Acc. is Zero after operation, reset otherwise. S: Set if most significant bit of Acc. is 1 after operation, reset otherwise. Example: If an addition operation is performed between 15 (BCD) and 27 (BCD), simple decimal arithmetic gives this result: 15 +27 ---- 42 But when the binary representations are
One of the idiosyncracities of the Z80 instrcution set is that the A register is not written as it is with ADD, viz ADD A C but SUB C. In addition although there are 16 bit ADD's there are no 16 bit SUB's. (16 bit subtraction is done using the SBC instruction.) The flags are set as follows C or carry flag 1 if answer <0 else 0 Z or zero
31 Oct 2014 AND is an instruction that takes an 8-bit input an compares it with the accumulator. It checks to see if both are set. If either one is reset, the resulting bit in the accumulator is zero. 0 and 0 result: 0 0 and 1 result: 0 1 and 0 result: 0 1 and 1 result: 1
31 Oct 2014 Or is an instruction that takes an 8-bit input an compare sit with the accumulator. It checks to see if anything is set, and if neither are set, it results in a zero. 0 and 0 result: 0 0 and 1 result: 1 1 and 0 result: 1 1 and 1 result: 1. Syntax. OR op8. Allowed Instructions. or a or b or c or d or e or h or l or ixh or ixl or iyh
C, ret nz, pop bc, jp nz,**, jp **, call nz,**, push bc, add a,*, rst 00h, ret z, ret, jp z,**, BITS, call z,**, call **, adc a,*, rst 08h. D, ret nc, pop de, jp nc,**, out (*),a, call nc,**, push de, sub *, rst 10h, ret c, exx, jp c,**, in a,(*), call c,**, IX, sbc a,*, rst 18h. E, ret po, pop hl, jp po,**, ex (sp),hl, call po,**, push hl, and *, rst 20h, ret pe, jp (hl)
Annons