Difference between revisions of "Z80:Opcodes:JR"
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<!-- Syntax for this instruction --> | <!-- Syntax for this instruction --> | ||
| − | + | JR NN ;unconditional jump | |
| − | + | JR cond.,NN ;conditional jump | |
=== Allowed Instructions === | === Allowed Instructions === | ||
| Line 14: | Line 14: | ||
;Constants | ;Constants | ||
| − | + | JR NN ;no condition | |
JR C,NN ;jumps if C is set | JR C,NN ;jumps if C is set | ||
JR NC,NN ;jumps if C is reset | JR NC,NN ;jumps if C is reset | ||
| Line 29: | Line 29: | ||
<!-- What the instruction can be used for --> | <!-- What the instruction can be used for --> | ||
== T-States == | == T-States == | ||
| − | cc is condition: NZ, Z, NC, C | + | cc is condition: NZ, Z, NC, C (PO, PE, P, M are not available) |
{| class="wikitable" | {| class="wikitable" | ||
| X || 12 | | X || 12 | ||
Latest revision as of 18:31, 19 March 2017
Relative jumps to the address. This means that it can only jump between 128 bytes ahead or behind. Can be conditional or unconditional. JR takes up one less byte than JP, but is also slower. Weigh the needs of the code at the time before choosing one over the other (speed vs. size).
Syntax
JR NN ;unconditional jump JR cond.,NN ;conditional jump
Allowed Instructions
;Constants JR NN ;no condition JR C,NN ;jumps if C is set JR NC,NN ;jumps if C is reset JR Z,NN ;jumps if Z is set JR NZ,NN ;jumps if Z is reset
Effects
All flags preserved.
Uses
T-States
cc is condition: NZ, Z, NC, C (PO, PE, P, M are not available)
| X | 12 |
| condition met | condition not met | |
| cc,X | 12 | 7 |
See Also
BIT,CALL,CP,CPD,CPDR,CPI,CPIR,DJNZ,JP
