Difference between revisions of "Z80 wait instructions"

Revision as of 00:22, 3 March 2024

Z80 instruction set that don't change registers value (except for F register):

Inst.	TS	Bytes	Flag modification
`NOP`	5	1	None
`CP (HL)`	8	1	C, S, and Z flags modified by definition. P/V detects overflow.
`NOP NOP`	10	2	None
`LD R,A`	11	2	C is preserved, H and N are reset, and alters Z and S. P/V is set if interrupts are enabled, reset otherwise.
`NOP CP (HL)`	13	2	C, S, and Z flags modified by definition. P/V detects overflow.
`BIT 0,(HL)`	14	2	Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.
`NOP NOP NOP`	15	3	None
`NOP LD R,A`	16	3	C is preserved, H and N are reset, and alters Z and S. P/V is set if interrupts are enabled, reset otherwise.
`NOP NOP CP (HL)`	18	3	C, S, and Z flags modified by definition. P/V detects overflow.
`NOP BIT 0,(HL)`	19	3	Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.
`NOP NOP NOP NOP`	20	4	None
`CP (IY+0)`	21	3	C, S, and Z flags modified by definition. P/V detects overflow.
`BIT 0,(IY+0)`	22	4	Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.
`NOP CP (IY+0)`	26	4	C, S, and Z flags modified by definition. P/V detects overflow.
`NOP BIT 0,(IY+0)`	27	5	Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.

@@ Line 5: / Line 5: @@
 | <tt>NOP</tt>         ||  5 || 1 || None
 |-
-| <tt>OR 0</tt>        ||  8 || 2 || C and N flags cleared, P/V detects parity, and rest are modified by definition.
+| <tt>CP (HL)</tt>     ||  8 || 1 || C, S, and Z flags modified by definition. P/V detects overflow.
 |-
 | <tt>NOP<br/>NOP</tt> || 10 || 2 || None
@@ Line 11: / Line 11: @@
 | <tt>LD R,A</tt>      || 11 || 2 || C is preserved, H and N are reset, and alters Z and S. P/V is set if interrupts are enabled, reset otherwise.
 |-
-| <tt>NOP<br/>OR 0</tt>|| 13 || 3 || C and N flags cleared, P/V detects parity, and rest are modified by definition.
+| <tt>NOP<br/>CP (HL)</tt>|| 13 || 2 || C, S, and Z flags modified by definition. P/V detects overflow.
 |-
 | <tt>BIT 0,(HL)</tt>  || 14 || 2 || Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.
@@ Line 18: / Line 18: @@
 |-
 | <tt>NOP<br/>LD R,A</tt>      || 16 || 3 || C is preserved, H and N are reset, and alters Z and S. P/V is set if interrupts are enabled, reset otherwise.
+|-
+| <tt>NOP<br/>NOP<br/>CP (HL)</tt>|| 18 || 3 || C, S, and Z flags modified by definition. P/V detects overflow.
 |-
 | <tt>NOP<br/>BIT 0,(HL)</tt>  || 19 || 3 || Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined.