-
rotating HL left through CarryI've tried this several ways, and it works for a while, then a particular value has a bit set in an inconvenient place and it all goes to pot. Eg: "…
...
ld de,temp
ex hl,de
ld (hl),d; (hl) = & ... rlca; a = &82, (hl) = &78
rld; ... a = &81, (hl) = &72
ld ... hl)
ld l,a
Course it does trash DE ... -
rotating HL left through CarryI've tried this several ways, and it works for a while, then a particular value has a bit set in an inconvenient place and it all goes to pot. Eg: "…
...
ld de,temp
ex hl,de
ld (hl),d; (hl) = & ... rlca; a = &82, (hl) = &78
rld; ... a = &81, (hl) = &72
ld ... hl)
ld l,a
Course it does trash DE ... -
rotating HL left through CarryI've tried this several ways, and it works for a while, then a particular value has a bit set in an inconvenient place and it all goes to pot. Eg: "…
...
ld de,temp
ex hl,de
ld (hl),d; (hl) = & ... rlca; a = &82, (hl) = &78
rld; ... a = &81, (hl) = &72
ld ... hl)
ld l,a
Course it does trash DE ... -
Help needed with a bit of code...My minds gone blank again I'm afraid, I'm having trouble with this routine that loads variables into memory then calls the corresponding routine. Th…
... get from the table into DE, point HL at your numerical data ... you want to preserve, then EX HL,DE to swap the pointers over ... POP those values again, DE and HL will be back as they ... , freeing up DE and HL for different tasks. And EX DE,HL can come in ... -
Help needed with a bit of code...My minds gone blank again I'm afraid, I'm having trouble with this routine that loads variables into memory then calls the corresponding routine. Th…
... ex hl, de
ld c,(hl)
inc hl
ld b,(hl)
dec hl ... ; assuming you need to preserve 'DE ... '
ex hl, de ... (bc),a
inc hl
[/code] Although ... -
How to disable the "scroll?" message?Hello. I'm a beginner Z80 assembly programmer and I decided to make a ZX Spectrum game to practice my skills and gain some more experience. I curr…
... no
LD (IX), HL
you have to do ... s no LD HL, DE either! I could use EX DE, HL since DE was not ... (and it did not allow EX HL, DE either).
You need to ... used:
ld (ix+nn),hl ; ld (ix+nn),l : ... +nn+1),h
ld hl,de ; ld h,d : ld ... -
Sort 2 byte words (x, y) on ypos, also question about swap (DE), (HL)Well that was a lot of debugging ;) But if you want a routine which takes an array of 16 byte words x, y and then sort them on y (ignoring x), I'm…
... hl, de
ld e, c
add hl, de
ex de, hl
pop hl
swap_word
pop af
pop hl ... e
push hl
add hl, de
pop de
ex de, hl
swap_word ... -
Z80: ABS(HL) functionI must be very tired but I cannot get my head around whether this function provides a correct implementation of a ABS function for a signed 16-bit va…
... br />
[code]
; Input: HL contains a signed 16-bit ... value
; Output: HL = ABS(HL)
ABSFunc:
BIT 7 ... perform a SBC HL, DE with HL containing 0 and DE the input value ... require a PUSH, POP, two EX DE, HL and something (OR A) to ... -
Pixel setting / general speccy codingi just started doing some cross-coding with the [url="http://www.bigfatpanda.fsnet.co.uk/z80.html"]Z80 SNA assembler[/url] and an emulator, and this …
... hl, de
ld e, (hl)
inc hl
ld d, (hl)
ex de, hl
srl e
add hl, de
ex de, hl
ld hl, pixelmsk
ld ...
ld b, (hl)
ex de, hl
ld a, (hl)
xor b ... -
Machine Code Sprites Example Code Using Char Based SystemBelow is my WIP code to do smooth screen wrapping sprites using char positions and offsets, as opposed to writing direct to a line (0-191) and shifti…
... 0
LD HL,gfx
ADD HL,DE
ps01:
HL,DE
DJNZ ps0
ps1:
EX DE,HL
LD A,(DE)
LD (HL),A
INC DE
INC ... -
IM2 Machine Code Sprites Example Code Using Char Based SystemFurther to my earlier post, here are sprites running using char method with IM2 driving it Note, for 48k spectrum using TASM [code] ; ***********…
... 0
LD HL,gfx
ADD HL,DE
ps01:
HL,DE
DJNZ ps0
ps1:
EX DE,HL
LD A,(DE)
LD (HL),A
INC DE
INC ... -
Smooth Color Masked Sprites using fast page flip on 48kHere is a quick demo of using char based sprites using the Page flip method: a) Background is copied to buffer b) Sprites drawn on buffer c) Buffer …
... +1), SP
EX DE, HL
LD SP, HL
EX DE, HL
LD ...
ADD HL,DE ; Add onto GFX
EX DE,HL ; Let DE now point to ... -
Smooth Masked Sprites using fast page flip on 48k Part 2Ok, After all the suggestions in Part 1, which were all excellent (Thankyou), I opted on the following: I have 2 x 6k Offscreen areas (Yes, that's …
... /> ADD HL,DE ; Add onto GFX
EX DE,HL ; Let DE now point ... /> LD HL,0
LD DE,16
ADD HL,DE
... /> LD HL,0
LD DE,16
ADD HL,DE
... -
Smooth Screen Scrolling RoutineHi everyone, this is a follow up to the thread on smooth screen scrolling. As promised here is the code for the routine. It's pretty long and fairl…
... L,E
EX DE,HL ;DE = SCREEN ADDRESS AGAIN
SBC HL,BC
EX DE,HL ;DE = SCREEN ADDR.
EX AF,AF ... NZ,CLOOPB
EX DE,HL ;DE = SCREEN ADDR.
ZERO ... -
Mode 2 Tile Editor SourceA Timex Mode 2 Tile Editor incorporating a byte mirror table. The compiled version is available in the CSSCGC 2008 collection from the WoS archive. …
... jr nz,cp2b_a ;
ex de,hl ; used to copy block to ... jr nz,cp2b_b ;
ex de,hl ; used to copy block to ... br /> ld hl,mirror_tbl ;
add hl,de ;
ld a,(hl) ;
... ld c,l ;
ex de,hl ; start of channel data to ... -
RFC: 64 column font codeIn BASIC, type CLEAR 49999 then import the code at 50000. Then type RANDOMIZE USR 50000. This will create a new channel and attach stream #4 to it. A…
... /> ; in HL
ex de,hl ; store the offset in DE
ld hl,$5c10 ... hl,de ; add the offset
ex de,hl ; put the result back in DE ...
; HL now points ... -
help sought with first foray into machine code - pixel scrolldownI have started to code my first machine code program, a simple roadrace game. I've based it around the pixel scrolldown routine in 40 Best Machine Co…
... 255 into accum??
sbc hl,de ;move pointer of line to ... /> ex de, hl ;put 224 into hl, byte to be copied into de
pop hl ... a char
add hl, de ;goto next line through a ... . . .
add hl, de ;to posn to be copied
ex de,hl ;?? but now ... -
CHANS system variableI modified my original code to incorporate Woody's changes and avoid using the stack: [code] org 60000 save_registers: push hl push de push bc …
... br /> save_registers:
push hl
push de
push bc
sbc hl, de ; calculate how much to add ... br /> ex de, hl ; start of channel data to HL
dec hl
... /> pop bc
pop de
pop hl
ret ... -
Common pitfalls and solutionsLet's discuss some of the common problems in Speccy programming, and the methods we use to avoid them. For an example, here is a piece of code that …
... /> LD HL,#1BB0
PUSH HL
LD HL,(#5C4F)
LD DE,#000F ...
ADD HL,DE
LD DE ... ,#1B5E
EX DE,HL ... -
A fast DRAW routineI was investigating how to speed up the line drawing for the [URL="http://www.worldofspectrum.org/forums/showthread.php?t=20225"]BASIC compiler[/URL]…
... H, L
push hl
ex de, hl ; D,E = y2, ... y2
exx
add hl, de ; error -= dX
bit ...
exx
add hl, de ; error -= dY
...
ld de, (SCREEN_ADDR)
add hl, de ;; Final screen addr ... -
automatic relocating of non-relocatable codeI was pondering upon the problem of changing absolute addresses used by CALL, JP, etc. when code is moved, without reassembling at the new location; …
... /> add hl,bc
ex de,hl
pop hl
add hl,bc
ex de,hl ;HL=address ... of location to change
ld (hl),e ;DE ... -
Tile based graphics and scrolling thingy...Here's my best attempt so far at a tile based rendering and scrolling routine. It draws in 22 8*8 graphics tiles along the top of the screen (junk i…
... hl,hl ; ASCII code * 8
add hl,hl
add hl,hl
ld de ... , faster!
add hl,de
ex de,hl ; Put the result in ... DE for draw routine
Undefine functionHere's a routine to selectively remove variables from the VARS area and reclaim the space. This can be done partially from BASIC already by assigning…
... br /> sbc hl,de
inc hl
ld a,(hl) ;initial ... control
NOTFOR: ex de,hl
add hl,bc
ld ... )+(length of variable)
ex de,hl ;HL=address of variable
...joining lines of BASICDue to overwhelming demand - well, one demand - well, more of a suggestion, really - here's a routine to join together lines of BASIC. The vertical c…
... /> EX DE,HL ;DE=new cursor position
LD HL,(23641) ;E_LINE
SBC HL,DE
hl
ex de,hl
add hl,bc ;HL=joined length
ex de,hl
ld (hl),e ...editing strings with INPUT LINEHere's the latest in my unpredictable series of utility routines. This one I needed for the SAGE game editor; it emulates INPUT LINE l$ but with the …
... pop bc
pop hl
ld de,(WORKSP)
ld ... workspace
NOTEXT: ex de,hl
ld (hl),$0d ;followed by ... ld hl,(STKBOT)
ld de,(WORKSP)
scf
sbc hl,de< ...Inefficient code in ROM, from ram-check to RAM-DONEHere is the inefficient code: [CODE] ;; ram-check L11DA: LD H,D ; Transfer the top value to the HL register LD L,E …
... - prepare to subtract.
SBC HL,DE ; subtract and add back setting ...
ADD HL,DE ; carry when back at ... /> [CODE]
;; ram-check
EX DE,HL
;; RAM-FILL
BeepFX ProblemHi All, I'm currently trying to integrate the BeepFX engine in my 100% Assembler Game and it plays the sound fine, but then plays the sound again, a…
... /> add hl,bc
ld a,(hl)
inc hl
... pop bc
SFXRTl1: add hl,de
ld a,h
ex de,hl
add hl,bc
ex de,hl
pop ...Optimisations in Exomizer Z80 decrunch codeThis is the 163 bytes old code (simple and optimized): [CODE] ld iy, exo_mapbasebits ld a, 128 ld b, 52 push de exo…
...
add hl, de
ex de, hl
inc iy
pop hl
djnz ...
add hl, de
ex de, hl
inc iyl
pop hl
dec ...Rotronics Wafadrive v.1.80 ROM - Corrupt or purposely broken?I've been digging around the Wafadrive v1.80 ROM (from [URL="http://zxspectrum.it.omegahg.com/_RO.htm"]here[/URL]) and can't decide if the ROM is cor…
... /> ;
l_0d09: inc hl
push hl
ld (iy+$00 ... /> push de
ld hl, $009f
ex (sp), hl
push hl
... /> add hl, de
ld e, (hl)
inc hl
ld h, (hl)
pop de
jp (hl)
;; hook- ...Movin And A Groovin Horizontal Flip improvementOn the left is the flip horizontal portion from Andy Pennell'S excellent Movin' & a Groovin' machine code screen routines from Your Spectrum #19 (Oct…
...
ADD HL,DE ADD HL,DE
ADD IX,DE ADD IX,DE
DJNZ ... /> FLATTR LD A,(HL) flattr LD A,(HL)
EX AF,AF' ; no ...
