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When would you use LD A,R ?Can anyone tell me a practical use of LD A,R and LD R,A I am confused when you would need to use it? Cheers
Can anyone tell me a practical use of LD A,R and LD R,A I am confused when you would need to use it?
Cheers -
Using R as a loop counterThis is just something silly I've found a while back. xD [b][How-to][/b] Setup your routine like this:[code] ld a,X ;see below ld r,a loop ;your …
... /> ld r,a
loop
;your routine here
ld a,r
ld a,r: jr nz,loop' commands) ... ld r,a
.l2
nop
inc b
ld a,r
jr nz,.l2
ld a,b
out (#FE),a ... -
DEC BC/LD A,B/OR C/JP NZ,loopyesterday i saw nice trick:[code] dec bc ld a, b or c jp nz, loop can be replaced (bc starts >255, short jump) by: dec bc inc b djnz loop [/code] …
yesterday i saw nice trick:[code]
dec bc
ld a, b
or c
jp nz, loop
can be replaced (bc starts >255, short jump) by:
dec bc
inc b
djnz loop
[/code]
..nice -
Programming MC : first stepsIsn't nice to collect all kinds of short routines to help making the first steps into MC for everyone who never touched MC? What I mean is mostly th…
... on screen
A simple Randomgenerator (not LD A,R)
Other tips and ... tricks.
Reading a value from a table ... ),hl ; store next RND-pointer
ld a,(hl) ; fetch RND number
marge ... -
Any played F.E.A.R? (New PC Game)I know a lot of you played Half-Life2 when it came out so I would gather a guess that a lot of you have been looking forward to this too (it's been a…
I know a lot of you played Half- ... so I would gather a guess that a lot of you have ... it's either F.E.A.R. or Quake 4 but I ... -
W.A.R. (missing artist?)[URL="http://www.worldofspectrum.org/infoseekid.cgi?id=0005620"]W.A.R.[/URL] NAK or MAK lower right ... might be MAK = Mark A. Jones? (already credi…
... /infoseekid.cgi?id=0005620"]W.A.R.[/URL]
NAK or ... right ... might be MAK = Mark A. Jones? (already credited)
A.R..gif[/img] -
Contention: LDI vs LD (ss), rAccording c.s.s. FAQ: instruction LD (ss),r breakdowns as pc:4,[b]ss:3[/b] and LDI as pc:4,pc+1:4,hl:3,[b]de:3,de:1 x 2[/b] can anyone explain why …
... . FAQ:
instruction LD (ss),r breakdowns as pc:4,[b ... -
Canny use of the 'r' register?Seeing Sokurah's code in the [URL="http://www.worldofspectrum.org/forums/showthread.php?p=583188#post583188"]crunch sound thread[/URL] has made me th…
... made me think about the r register.
... I've used this a fair bit myself as an ... way to get a 'random' number eg:
ld a,r
... so presumably better than eg LD A,(23672) (though much much ... how it's a bit of a blunt instrument as ... -
New WIP from Kabuto Factory: A.R.C.O.S.Hi everybody! After a long time in silence (...you know, life and its commitments...), we're coming back with new WIP for Speccy: A.R.C.O.S., a new …
Hi everybody!
After a long time in silence (...you ... new WIP for Speccy: A.R.C.O.S., a new "brick'em ... [/url]
Here goes a screenshot ;)
[IMG]http ... -
New game from Kabuto Factory: "A.R.C.O.S."Hi everybody! After almost one year in production (...well... not so much... :roll:), we've got new release: A.R.C.O.S., a brick'em all with some sh…
... got new release: A.R.C.O.S., a brick'em all with ... possible. You control A.R.C.O.S., a spaceship which bounces an ... lives. In addition, A.R.C.O.S. has a laser blast with ... extra ammo when you clear a stage, depending on the ... our fellow RALF (thanks a lot, dude!) -
A FAQ from a Z80 datasheet may reveal some up-to-now unknown behavioursA fellow member of the zonadepruebas.com forum has just mailed this PDF to me. [url]http://www.atc.us.es/~rodriguj/zilog_z80_faq.zip[/url] It's an e…
A fellow member of the ... It's an exceprt from a 1995 Z80A datasheet. This FAQ ... do cycle step on a NMOS o CMOS chip?< ... - What happens if a NMOS Z80 suffers a negative spike? (those pesky ... behaviour of interrupts during a LD A,I or LD A,R instructions? (this may ... -
R registerI'm cross-posting this as a spin-off of a [url="http://www.worldofspectrum.org/forums/discussion/52748/zx-spectrum-cartridges/p2"]thread in "Hardware…
... /> The Z80 CPU contains a memory refresh counter, enabling dynamic ... programmed, resulting from an LD R, A instruction.
The data ... fetch. Hence R register can be considered a simple counter ... on), increment twice for "LD A,R" instruction, and once for ... -
Pocket Clive - 2 QuestionsHello, I've just started using Pocket Clive on my iPaq pocket PC, excellent emulator BTW. 1. I have just wrote a small BASIC program to randomly pi…
... on subsequent calls to the RND function, making it not very ... (RND*n)+1
110 PRINT a(p);" ";
120 LET a(p)=a ... once every 20ms)
ld b,a
ld a,r ; the refresh register is ... -
Bug fixing woesGaahhhh! I've spent an afternoon off work agonizing over why my routine didn't work. It's something I'd already restarted so didn't want to wipe th…
... Patrick Rak's Xor shift rnd generator, but stupidly forgot it ... />
[CODE]
call rnd
ld (hl),a
[/CODE]
a (variable) or ld a,r. This oversight meant I ... -
MC LPRINT 23681Having problems with this routine to print large on the screen using LPRINT, it works ok in BASIC, but cant seem to get it to loop for some reason in…
... /> 2) Use the ROM's RND function.
3) Read values ... ,22816 ;random colours
ld b,159
ld a, r
and 0x37 ... ROM
ld d, a
ld a, r
ld e, a
lp2: ld a, (de)
Short Z80 QuizQ1) Which program gives different result ? A) XOR A ADD A,A B) XOR A ADC A,A C) SCF ADD A,A D) SCF ADC A,A Q2) What is the equivalent of NEG …
... of NEG ?
A)
LD A,-1
B)
A)
LD B,10
LD HL,60000
DEC BC
LD A,B
OR C
Q8) What value holds A after LD A,R ?
Q9) What ...InterruptsA small piece intended for the FAQ. Comments, corrections, additions welcome. Notably: * How long does the 48K ULA hold /INT low? * What happens i…
... can be missed entirely. A second effect can occur with ... :
* If a LD A,I or LD A,R (which copy IFF2 to ... interrupt' feature is known as a retriggered interrupt.
... it was zero (thus causing a reset). However various peripherals, ...Mysterious bit of codeHi everyone, I found the follow piece of code in a game and was wondering what it does. ld bc,40ffh ld e,40h loop ld a,r …
... follow piece of code in a game and was wondering what ... /> ld bc,40ffh
ld e,40h
loop ld a,r
in a,(c ... ages, and then returns.
A delay of some kind, I ...Urgent Help needed to fix this: calling all machine code gurusI am currently trying to write tutorials on the amazing Orfeus music composer by Proxima which allows you to do multi channel music through the beepe…
... /> ld a,#00
ld (l8994+1),a
ld (l899d+1),a
ld (l89e3+1),a ... a
ld (l8bd9+1),a
inc a
ld (l898F+1),a
ld a,(l8994 ... ),a
ld e,a
ld a,
robpearmain
November 2006
Development
Machine code loopsThis might sound a bit daft, but I,ve forgotten how to do loops using th 'b' register... I want to loop this x mount of times: [CODE]ld a,r and 6 i…
This might sound a bit daft, but I,ve ... /> [CODE]ld a,r
and 6
inc a
ld (aa+1),a
Accidental rainbow effects.. How do I adapt?I've somehow bizzarrely created a rainbow text effect on my title screen by accident. The title was just supposed to flash different colours whilst …
I've somehow bizzarrely created a rainbow text effect on my ... ]org 60000
loop ld a,239
in a,(254) ;check keys ... /> start ret ;return
flash LD A, R ;flash routine
AND 67 ... A
LD B, 14
LD DE, 22665
lp2 LD (DE), A
Idk>le me browsing through some game's code >..... [code]61A8 F5 push af 61A9 3EFF ld a,FF 61AB D37F out (7F),a 61AD D33F ou…
... ED57 ld a,i
61DA 67 ld h,a
61DB ED5F ld a,r
61DD 6F ld l,a
ld i,a
62A9 7D ld a,l
62AA ED4F ld r,a
Trouble with rainbow effect push/popI'm having a bit of bother getting my rainbow graphics to behave themselves. Basically I want a rainbow effect to last for say 4 seconds before movi…
... /> loop1 di
ld a,233
in a,(254)
;push bc ... loop1
ret
flash LD A, R ;rainbow flash routine
AND ... lp2
RET
flash2 LD A, R ;rainbow flash routine
AND ...MC LPRINT 23681Having problems with this routine to print large on the screen using LPRINT, it works ok in BASIC, but cant seem to get it to loop for some reason in…
... /> call cols ;fill attributes
ld hl,72 ;start of address ... br /> ret
print ld a,3 ;channel 3 printer
ld b,159
lp2 ld a,r
and 5
inc a
ld ... (hl),a
inc ...Unusual custom turbo loaders - with sourcesI have always been fascinated by turbo loaders; my games all feature a TZX version with one of such schemes implemented, and I have been experimentin…
... 65491
LD A,C
CPL
LD C,A
LD A,R
AND ... 007
OR 008
OUT (254),A ... br /> LD A, H
XOR L
LD H, A
LD A, D< ... 65491
LD A, C
CPL
LD C, A
LD A, B
Simple text scrolling routine...I'm having trouble writing a very simple text scroller, the idea is to use the ROM printer routine to print 32 characters each time the routine is ca…
...
ld a,(counter)
inc a ;increase
ld (counter),a ;update counter ... ld hl,23264
ld b,64
loop
ld a,r< ... br /> and 5
inc a ...
ld (hl),a
ZEsarUX 6.1 RCHi I have uploaded a new beta version of ZEsarUX. This is ZEsarUX 6.1 RC so next version will be a final stable version :) You can download it fr…
... emulation (experimental)
Added a fast spectrum core (with some ... Improved menu interface:
* added a setting to limit menu event ... opcodes
* Added a setting to start TBBlue directly ... reading it by using LD A,R and LD A,I affected many demos ...ZEsarUX-7.0Hi! I have uploaded a new ZEsarUX stable version :) This is ZEsarUX 7.0 There are a lot of new features added, more than ever! You can downl…
... />
I have uploaded a new ZEsarUX stable version :)
* Added a setting to start TBBlue directly ... utils to paste contents to a file
Improved frameskip: ... reading it by using LD A,R and LD A,I affected many demos< ...
