Shift and Rotate
Before I start to teach you the shift and rotate instructions. You probably want to review the bit placements. You'll need to look at the bit place names especially. Each of these shift and rotate commands rotates one bit to the left or right.
There is only really one difference between the shift and rotate instructions: rotate cycles the bits around going out one side and coming in the other, while shift rotates the bits out one side or the other leaving the space where the rotated bits where either unchanged or zeroed.
rl
rl arg1 - Rotates arg1 register to the left
with the carry's value put into bit 0 and bit 7 is put into the carry.
rl d rl (hl) rl (iy+02) rl (ix+3)
rla
rla - Rotates a register to the left with the carry's
value put into bit 0 and bit 7 is put into the carry. One byte shorter
than rl a.
rla
rlc
rlc arg1 - Rotates arg1 to the left with bit
7 being moved to bit 0 and also stored into the carry.
rlc (hl) rlc (iy+5) rlc (ix+$10) rlc a
rlca
rlca - Rotates a to the left with bit 7
being moved to bit 0 and also stored into the carry. It's one byte
shorter than rlc a.
rlca
rr
rr arg1 - Rotates arg1 to the right with
the carry put in bit 7 and bit 0 put into the carry.
rr (hl) rr b rr (ix+5) rr (iy+$00)
rra
rra - Rotates a to the right with the carry
put into bit 7 and bit 0 put into the carry flag. It's one byte
shorter than rr a.
rra
rrc
rrc arg1 - Rotates arg1 to the right with
bit 0 moved to bit 7 and also stored into the carry.
rrc (hl) rrc (ix+3) rrc (iy+$09) rrc e
rrca
rrca - Rotates arg1 to the right with bit 0 moved to bit 7
and also stored into the carry. This is one byte shorter than rrc a.
rrca
sla
sla arg1 - Shifts arg1 register to the left with
bit 7 moved to the carry flag and bit 0 reset (zeroed).
sla (hl) sla (iy+$08) sla (ix+3) sla e
sra
sra arg1 - Shifts arg1 register to the right with
bit 0 moved to the carry flag and bit 7 retaining it's original value.
sra (hl) sra (ix+0) sra (iy+200) sra h
srl
srl arg1 - Shifts arg1 register to the right with
bit 0 moved to the carry flag and bit 7 zeroed.
srl (hl) srl (ix+$fe) srl (iy+32) srl c
More from z80 » Advanced
All The Ports // APD // Assembler Directives // Entry Stack // User Fonts // IM 1 // IM 2 // Index, Shadow, and Other Registers // User Interrupt // Morphic Code // On-Off // Reading Keypresses from Port // Shift and Rotate // Simulating Key Presses // Sound // Square-Root Programs // System Flags of TI-OS