ped7g

; (C) [copyleft] 2018 Peter Helcmanovsky
; License: CC0 https://creativecommons.org/share-your-work/public-domain/cc0
;
; x86_64 linux asm example of fixed-point arithmetic
; (see https://en.wikipedia.org/wiki/Fixed-point_arithmetic)
;
; to build I'm using nasm and ld:
; nasm -f elf64 %f -l %n.lst -w+all; ld -b elf64-x86-64 -o %n %n.o
; (where %f is source file name and %n is just the main part w/o extension)
;

ped7g

    DEVICE ZXSPECTRUM48
    OPT reset --zxnext=cspect --syntax=abfw
    ORG     $8000
start:
    ;; FIRST test: black border configured into default transparency fallback colour, inkmask 7
    ; black border
    xor     a
    out     (254),a
    ; configure the NextULA palette (inkmask 7, select ULA palette for write, display first pals, enable NextULA mode)
    nextreg $42,$07 ,, $43,%0'000'0'0'0'1

ped7g

; syntax for https://github.com/z00m128/sjasmplus/releases assembler
    OPT --syntax=abfw --zxnext

;;----------------------------------------------------------------------------------------
;; reads nextreg in A into A

ReadNextReg:
        ; Input
        ;       A = nextreg to read
        ; Output:

ped7g

LimitHlValue:
  ; In: HL = value to be clamped to -0x100 .. +0x100
  ; Out: HL = clamped value
  ; Uses: A + flags
  ; (this is not mathematically correct, values 0x7F?? clamp to -0x100, for performance reasons)
    ld  a,h
    inc a
    sra a           ; will be 0 for -256..+255 (+256 will get "clamped")
    ret z
    ld  hl,0x100

ped7g

        OUTPUT "ECHO"
        ORG     8192
Start:  ex      de,hl
        ld      a,d
        or      e
        ret     z       ; DE == 0, no pointer to arguments
Print:  ld      a,(de)
        or      a
        ret     z       ; zero byte end of command line
        cp      13

ped7g

REAL_ORG = #3c51
DICT_BEGIN = #3c49
DATA_REG = 129
CONTROL_REG = 128
RTS_LOW = #16
RTS_HIGH = #56

    MACRO CHECKSUM start?
        opt push listoff    ; disable listing while calculating checksum
.ptr = start?

ped7g

    DEVICE ZXSPECTRUMNEXT
    ORG $8000   ; this example does map Bank5/Bank7 ULA to $4000 (to use "pixelad" easily)
mainLoop:
    call FlipULABuffers ; flip the buffer screen to visible screen and flip buffer
    call drawDot
    jr mainLoop

FlipULABuffers:     ; Flip ULA/Alt ULA screen (double buffer ULA screen)
;     ret ; uncomment to see effect of non-double-buffered running (blinking dots)
    ld a,(ULABank)  ; Get screen to display this frame

ped7g

    DEFINE USE_DMA_TO_CLEAR_SCREEN  ; comment out to get LDIR clear version
    DEFINE USE_DOUBLE_BUFFERING     ; comment out to see single-buffer redraw issues

    DEVICE ZXSPECTRUMNEXT

BORDER  MACRO color?
            ld  a,color?
            out (254),a
        ENDM

ped7g

; show how 8-bit color values RRRGGGBB are being extended to full 9-bit definition
; displays blue squares with 8bit blue part 0, 1, 2, 3 (all possible blue shades in 8b)
; and under them the 9bit defined blues as %000, %011, %101, %111 (how 8b extends to 9b)
; assembling: sjasmplus color8vs9b.asm  ( https://github.com/z00m128/sjasmplus )

    DEVICE ZXSPECTRUMNEXT : OPT --syntax=abfw
    ORG $8000
start:
    di
    ld      a,7

ped7g

; to assemble: sjasmplus asterisk_vs_exclamation_char.asm
    DEVICE ZXSPECTRUM48,31999 : OPT --zxnext

    ORG $8000
font:
    ASSERT 0 == high(font) % 8    ; must reside at aligned-enough address to fit this
    ds '!'*8,0      ; don't bother to define other chars, go to exclamation mark
    dg ---##---
    dg ---##---
    dg ---##---