Difference between revisions of "Z80 Routines:Optimized:addAtoHL"

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[[Category:Z80 Routines|AddAtoHL]]
 
[[Category:Z80 Routines|AddAtoHL]]
  
This is an optimized addAtoHL because it is a little faster and doesn't need other 16-bit register.
+
This is an optimized addAtoHL. It is a little faster and doesn't need another 16-bit register.
  
Also it can be changed to add A to any 16-bit register. The only down is 1 extra byte.
+
Also it can be changed to add A to any 16-bit register. The only down side is one extra byte.
  
Use it as a subroutine (don't forget the ret) or a macro.
+
Use it as a subroutine (don't forget the ret) or macro.
  
 
Normal way:
 
Normal way:
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add a,l
 
add a,l
 
ld l,a
 
ld l,a
adc a,h    ;^ this two line
+
adc a,h    ;^ these two lines
 
sub l      ;v increase h if there is carry
 
sub l      ;v increase h if there is carry
 
ld h,a
 
ld h,a
 
;5 bytes and 20 clock cycles
 
;5 bytes and 20 clock cycles
;but no other 16-bit register pair messed
+
;but no other 16-bit register messed up
 
  </nowiki>
 
  </nowiki>
  
 
Thanks to CoBB.
 
Thanks to CoBB.

Revision as of 17:06, 7 November 2009


This is an optimized addAtoHL. It is a little faster and doesn't need another 16-bit register.

Also it can be changed to add A to any 16-bit register. The only down side is one extra byte.

Use it as a subroutine (don't forget the ret) or macro.

Normal way:

	ld d,$00
	ld e,a
	add hl,de
;4 bytes and 22 clock cycles
 
addAtoHL:
	add a,l
	ld l,a
	adc a,h    ;^ these two lines
	sub l      ;v increase h if there is carry
	ld h,a
;5 bytes and 20 clock cycles
;but no other 16-bit register messed up
 

Thanks to CoBB.