Programming:Next / previous line calculation: Difference between revisions
Created page with "= Next line = This routines calculate the next line from the given address. == Firmware == '''Input:''' HL=Address '''Output:''' HL=Address of the next line '''Destroyed:'''..." |
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'''Output:''' HL=Address of the next line | '''Output:''' HL=Address of the next line | ||
'''Destroyed:''' AF | '''Destroyed:''' AF,BC | ||
<pre> | <pre> | ||
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add h | add h | ||
ld h,a | ld h,a | ||
ret nc | |||
ret | ld bc,#c050 | ||
ld bc, | add hl,bc | ||
ret | ret | ||
</pre> | </pre> | ||
Revision as of 09:47, 17 April 2015
Next line
This routines calculate the next line from the given address.
Firmware
Input: HL=Address
Output: HL=Address of the next line
Destroyed: AF
SCR_NEXT_LINE equ #BC26 call SCR_NEXT_LINE
Without Firmware
Input: HL=Address
Output: HL=Address of the next line
Destroyed: AF,BC
; Richard Fairhurst
; October 1997
;
;*** Next line down from HL ***
.nline ld a,8
add h
ld h,a
ret nc
ld bc,#c050
add hl,bc
ret
Previous line
This routines calculate the previous line from the given address.
Firmware
Input: HL=Address
Output: HL=Address of the previous line
Destroyed: AF
SCR_PREV_LINE equ #BC29 call SCR_PREV_LINE