;; This example shows a simple raster using the CPC+ ;; extended palette, and using the CPC+ programmable ;; raster interrupts to define the position of the raster ;; on the display. ;; ;; This example is designed for CPC+ only and will ;; not work on the CPC or KC Compact. ;; ;; This example will compile with the MAXAM assembler ;; or the built-in assembler of WinAPE32. .scr_set_mode equ &bc0e org &8000 nolist ;;-------------------------------------------------- ;; clear screen ld a,1 call scr_set_mode ;;-------------------------------------------------- ;; STEP 1 - Unlock CPC+ additional features di ld b,&bc ld hl,sequence ld e,17 .seq ld a,(hl) out (c),a inc hl dec e jr nz,seq ei ;;---------------------------------------------------------- ;; STEP 2 - Install a interrupt handler ;; disable interrupts di ;; interrupt mode 1 (call to interrupt handler at &0038) im 1 ;; &c9 corresponds to the opcode RET ;; &fb corresponds to the opcode EI ;; ;; RET opcode takes 3us, EI opcode takes 1us ;; write EI,RET to interrupt handler at &0038 ld hl,&c9fb ld (&0038),hl ;; enable interrupts ei ;;---------------------------------------------------------- ;; STEP 3 - Initialise CPC+ Programmable Raster Interrupt ;; disable interrupts di ;; page-in asic registers to &4000-&7fff ld bc,&7fb8 out (c),c ld a,100 ;; line 100 ld (&6800),a ;; set line ;; page-out asic registers ld bc,&7fa0 out (c),c ;; enable interrupts ei ;;------------------------------------------------------------ .main_loop ;; wait for interrupt halt ;; delay so that colour change is hidden by border defs 16 ;; page-in asic registers to &4000-&7fff ld bc,&7fb8 ;; [3] out (c),c ;; [4] ;; address of pen 0 in CPC+ ASIC registers ld de,&6400 ;; [3] ;; start of table ld hl,raster_colours ;; [3] ;; number of colours in table*2 ld b,end_raster_colours-raster_colours ;; [2] ;; /2 srl b .rl ;; read colour from table (a byte at a time) ;; write colour to ASIC colour palette (a byte at a time) ld a,(hl) ;; [2] ld (de),a ;; [2] inc hl ;; [2] inc e ;; [1] ld a,(hl) ;; [2] ld (de),a ;; [2] inc hl ;; [2] dec e ;; [1] ;; delay so that the next colour change occurs ;; immediatly below this colour change defs 64-2-2-2-1-2-2-2-1-1-3 dec b ;; [1] jp nz,rl ;; [3] ;; page-out asic registers ld bc,&7fa0 out (c),c jp main_loop ;;--------------------------------------------- ;; - there is two bytes per colour. ;; - these are stored in a form that can be written direct ;; to the CPC+ colour palette registers .raster_colours defw &0001 defw &0004 defw &0008 defw &000d defw &000f defw &000d defw &0008 defw &0004 defw &0001 defw &0000 .end_raster_colours ;;---------------------------------------------------------- ;; this is the sequence to unlock the ASIC extra features .sequence defb &ff,&00,&ff,&77,&b3,&51,&a8,&d4,&62,&39,&9c,&46,&2b,&15,&8a,&cd,&ee