-
Relocation with SDCCI desperately need auto- relocation with SDCC. Something that will compile all of my code using start address 0 and generate relocation table so that…
...
pop hl
pop bc
pop de
ex ... /> ; e = char c
; bc = size_t n
ld ... ) ; remember current char
cpi
jr z, match ; ... match:
dec hl ; cpi stepped hl one past last ... -
Experimenting with turboloadersHello, My first post, having lurked here for a while. I'm a lifelong computer nerd, Spectrum fan since childhood in the eighties, and have recently…
... checksum
pop bc ; fetch data ... /> dec bc ; decrement data length
push bc ; save ... .verify_checksum:
push bc ;exit code assumes data length ... -
Can a guy that traveled on the short bus learn machine code...Hmmm So after some soul searching I figured it was time to finaly nail spectrum machine code. Its so frustrating to sit infront of a basic listing w…
... /> After that its time to decrement the register.
At ... we are already playing with BC to clear the registers, why ... [/IMG]
Register Pair BC:
[code]
010200 ... ...
LD BC,0000
DEC BC
RET
Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... addresses in HL: use the CPI instruction, which performs a comparison ... ), then increments HL and decrements BC. It's designed for scanning ... the P/V flag when BC reaches zero, so you can ... /> ld bc, 1024
loop:
ld (hl), 62
cpi
Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... /> ld bc, 1024
loop:
ld (hl), 62
cpi
ld hl, 16384
ld bc, 1024
ld d, 62 ... :
ld (hl), d
cpi
jp pe, loop
Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
[QUOTE] ld hl, 16384
ld bc, 1024
loop:
ld (hl), 62
cpi
jp pe, loop
ret[/QUOTE]
Great trick!
I've never used CPI in my life before.
But I guess I'll be using it now :)Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... ld hl, 16384
ld bc, 1024
ld d, 62 ... /> ld (hl), d
cpi
jp pe, loop
ld bc, #1024
loop2:
ldi ... /> jp pe, loop2 ; Test bc and loop
ret
Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... nice, both the use of CPI, and the tweaking above. At ... /> ld hl, #byte_to_write
ld bc, #1024
loop2:
ldi ... "
jp pe, loop2 ; Test bc and loop
ret
Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... that doesn't show DEC BC/LD A,B/OR C ... . Whats the point of exploiting CPI when you do not know ...Assembly - Loops bigger than 255Hi, It looks like it's a bit difficult to make loops with more than 255 cycles on Z80 machine code, since the 16-bit decrements (DEC) do not alter a…
... that doesn't show DEC BC/LD A,B/OR C ... . Whats the point of exploiting CPI when you do not know ...mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
... ld hl,$stringstart
ld bc,$bytes
loop:
cpi
jp pe,loop
ld bc,$bytes
ld d,$ ... /> ld (hl),a
cpi
jp pe,loop
mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
... ld hl,StringAddress
ld bc,StringLength
.lp0
... /> ld (hl),a
cpi
jp pe,.lp0
ld bc,StringLength
.loop
... ld de,StringAddress
ld bc,StringLength
.lp0
...mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
This just sorta came up all of a sudden.
[code]InPlaceV2
ld hl,StringAddress
ld bc,StringLength
scf
.loop
rr (hl)
jr nc,.loop
cpi
jp pe,.loop
ret[/code]mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
... /> ld hl,StringAddress
ld bc,StringLength
scf
.loop ... )
jr nc,.loop
cpi
jp pe,.loop
mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
... /> ld hl,StringAddress
ld bc,StringLength
scf
.loop ... )
jr nc,.loop
cpi
jp pe,.loop
mirroring bitsIf I have a string of 1408 bytes, each of which has one bit 'b' set, what's the shortest way of mirroring that string, so that each bit set at positi…
... /> ld hl,StringAddress
ld bc,StringLength
scf
.loop ... )
jr nc,.loop
cpi
jp pe,.loop
How to print logo onto screen at chosen coordinates?Hi, I've just got back into zx spectrum games after all these years and after seeing some of the great games on here I would like to start learning p…
... of our font.
ld bc,728 ; 96 chars * 8 rows ... byte of new.
dec bc ; decrement counter.
ld a,b ... /> jr nz,font1 ; repeat until bc=zero.
ld hl,60000 ...Animated attribute revealA new challenge to solve next. I would like to create an animated attribute reveal in machine code by having my 768 byte attributes held in ram whic…
... of the difference and inc/decrement the attributes accordingly - but ... /> ld bc,0
ld (CHANGED),bc
ld bc,1024 ; ... INK_OK: ld bc,(CHANGED)
inc bc
ld (CHANGED),bc
ex ...Pac-Land: can be coloured?All versions of this game are full coloured, but not the Spectrum version. It has large sprites, but maybe the scroll is too fine to make a coloured …
... ;attribute area
LD BC,640 ;nr of chars < ... DE
CPI ;INC HL,DEC BC no change DE
BC=0
DrawBottomAttr ... bottom part
LD BC,160 ;nr of chars
CPI ;INC HL,DEC BC no change DE
LDI questionWhen using LDI (or LDD) is it possible to access the value that is transfered from (HL) to (DE), or does the Z80 use an internal data cache to store …
... .
PF flag Set if BC not 0.
SF, ZF ... 't work the same as CPI where the flags indicate if ... and Z flags like the CPI instruction does.Address bus contents (i.e. PC) during execution of HALTI'm wondering if anyone can tell me what's placed on the address bus during execution of HALT, beyond the initial M1 cycle. The Z80 user manual state…
... behaviour of the LDI and CPI instructions. As in this thread ... HL, the fifth is decrementing BC and PC.
So ...LDI questionWhen using LDI (or LDD) is it possible to access the value that is transfered from (HL) to (DE), or does the Z80 use an internal data cache to store …
... LDI is HEX A0
CPI is HEX A1
decrement DE and transfer byte/update ... 't work the same as CPI where the flags indicate if ... and Z flags like the CPI instruction does. [/QUOTE]
Double-Buffer ScreenFor my Alien Breed Speccy re-write I decided to use a Double Buffer (DB) or 'Back Screen' to draw all the game action onto, before shuffling the whol…
... /> call transfer_back_to_front
pop bc
inc c
... /> generate_screen_table:
;
ld bc,0 ; first clear the x ... , :)
dec d ; decrement the loop...
ld a ...
ld bc, screen_table ; remove this if you ...Sorting BusinessThis is a little bit different from the usual game-related fare but I know there are a few people here who like this sort of thing. This is about so…
... array_lo
; hl = array_hi
; bc = size
; ix = compare
add hl,bc
push hl ; save array_hi ... increment "balance". Whenever you decrement "j" also decrement "balance". Now change ...clear a windowed area of the screenHi everyone! Ain't been on here for donkeys, but have recently started messing around with a little game. I'm looking for ideas/opinions on the bes…
... ;: RANDOMIZE cols+256*rows: LET bc=USR ClearWindow
; row,col ... =rows
ld b,0 ;BC never exceeds 32, so B ... row
dec (ix+1) ;decrement rows counter
ret z ...Detecting flash mode inversionsIs is possible to detect with certainty when flashing characters change from normal to inverted and vice-versa?
... *8: PAUSE 8:
LET bc=USR 23296:
NEXT r ... ;: RANDOMIZE cols+256*rows: LET bc=USR FlashWindow
; row,col ... row
dec (ix+1) ;decrement rows counter
ret z ...ZERO Emulator - BugsI have been using Zero emulator to experiment a few routines in assembly, since it has a somewhat usable debugger. However I believe I found a few b…
... make similar use to "DEC BC", and actually detect a zero ... instructions have to repeat until BC==0 so they have ... and you want to 'dec bc' and repeat if not ... :
[code]
cpi
jp pe, loop_again
inc hl
dec bc
ld a,b
Subtract 4 from an addressThis is a novice Z80 question really: I'm trying to vertical scroll my back buffer, but I'm not sure of the quickest way to apply an offset and mo…
... a 256 bytes boundary, and decrement a single register only. Thus ... :
[code]
ld bc,26*256+26*18 ; repeat ... times, plus compensate LDD decrementing BC
loop:
REPT 18 ...Problem with BC corrupting after DJNZJust for fun, I'm messing around trying to get the level maps from Lemmings to display on the screen with machine code. It's been ages since I did an…
... LOOP PUSH DE
LD BC,32 ; SET THE COUNTER FOR ... POP DE
LD BC,32 ; 32 CHARS TO THE ... LINE
ADD HL,BC ; GET TO THE NEXT ... br /> JR NZ, LOOP ; DECREMENT THE LINE COUNTER AND LOOP ... ; NEXT ADDRESS
LD BC,511 ; 511 MORE CHAR SQUARES ...
