BIOS Screen Functions
From CPCWiki - THE Amstrad CPC encyclopedia!
Contents
Screen Init
BBFF SCR_INITIALIZE BC02 SCR_RESET
Screen Resolution
BC0E SCR_SET_MODE ;in: A=mode (0=160x200x16, 1=320x200x4, 2=640x200x2) BC11 SCR_GET_MODE ;out: A=mode (cy=mode0, z=mode1, ie. cmp mode,1)
Screen Palette
BC32 SCR_SET_INK ;in: A=index, B=color1, C=color2 BC35 SCR_GET_INK ;in: A=index, out: B=color1, C=color2 BC38 SCR_SET_BORDER ;in: B=color1, C=color2 BC3B SCR_GET_BORDER ;out: B=color1, C=color2 BC3E SCR_SET_FLASHING ;in: H=count1, L=count2 BC41 SCR_GET_FLASHING ;out: H=count1, L=count2
VRAM Address Translation
BC1A SCR_CHAR_POSITION ;in: H=x, L=y, out: HL=vram addr, B=bytes/char BC1D SCR_DOT_POSITION ;in: DE=x, HL=y, out: HL=vram addr, C=mask, DE, B BC20 SCR_NEXT_BYTE ;out: HL=HL+1 (wrapped within 800h-byte block) BC23 SCR_PREV_BYTE ;out: HL=HL-1 (wrapped within 800h-byte block) BC26 SCR_NEXT_LINE ;out: HL=HL+800h, or HL=HL+50h-3800h (or so) BC29 SCR_PREV_LINE ;out: HL=HL-800h, or HL=HL-50h+3800h (or so) BC2C SCR_INK_ENCODE ;in: A=color, out: A=color_mask BC2F SCR_INK_DECODE ;in: A=color_mask, out: A=color BC17 SCR_CHAR_LIMITS ;out: B=max_x(19,39,79), C=max_y(24)
Fill VRAM
BC14 SCR_MODE_CLEAR ;clear vram, set offset=0000h, update inks BC44 SCR_FILL_BOX ;in: A=fillbyte, H=x1, L=y1, D=x2, E=y2 BC47 SCR_FLOOD_BOX ;in: A=fillbyte, HL=vram addr, D=xsiz, E=ysiz BC5F SCR_HORIZONTAL ;in: A=pen, DE=x1, BC=x2, HL=y BC62 SCR_VERTICAL ;in: A=pen, HL=y1, BC=y2, DE=x
Further Stuff
BC4A SCR_CHAR_INVERT ;in: H=x, L=y, B=paper, C=pen
BC4D SCR_HARDWARE_ROLL ;in: A=paper, B=dir(0=down, FFh=up)
BC50 SCR_SOFTWARE_ROLL ;in: A=paper, B=dir(""), H=x1, L=y1, D=x2, E=y2
BC53 SCR_UNPACK ;in: HL=src, DE=dest (mono 8x8 char to colored 8x8)
BC56 SCR_REPACK ;in: H=x, L=y, A=pen, DE=dest (colored 8x8 to mono)
BC59 SCR_ACCESS ;in: A=drawmode (0=Normal, 1=XOR, 2=AND, 3=OR)
BC5C SCR_PIXELS ;in: HL=vram addr, C=xmask, B=color
BDE5 HOOK_SCR_READ ;in: HL=vram addr, C=xmask, out: A=color
BDE8 HOOK_SCR_WRITE ;in: HL=vram addr, C=xmask, B=color
BDEB HOOK_SCR_MODE_CLEAR ;clear vram, etc. (same as BC14)
BC05 SCR_SET_OFFSET ;in: HL.bit10..0 = vram offset 0..7FFh
BC08 SCR_SET_BASE ;in: A.bit7-6 = vram block 0..3
BC0B SCR_GET_LOCATION ;out: A.bit7-6=block, HL.bit10..0=offset
BD55 SCR_SET_POSITION_664 ;in: A=BASE,HL=OFFSET, out: A AND C0h, HL AND 7FEh
Machine Pack (Screen)
BD19 MC_WAIT_FLYBACK ;wait until/unless PIO.Port B bit0=1 (vsync) BD1C MC_SET_MODE ;in: A=video mode (0..2) (for C' and gate array) BD1F MC_SCREEN_OFFSET ;in: A=base, HL=offset (for CRTC) BD22 MC_CLEAR_INKS ;in: DE=ptr to border and 1 ink (2 bytes) BD25 MC_SET_INKS ;in: DE=ptr to border and 16 inks (17 bytes)
These functions are directly accessing I/O ports. WAIT_FLYBACK is eventually useful. The MODE/OFFSET apply the new setting to the hardware (but the BIOS functions like TXT_WR_CHAR aren't aware of it; so they do still draw pixels at the old offset and old color depth). The INK functions expect hardware color codes (eg. 14h or 54h for black), and, the infamous blink-feature will overwrite the new colors after soon.
