;; plot a pixel using the firmware screen functions scr_set_mode equ &bc0e scr_dot_position equ &bc1d scr_ink_encode equ &bc2c kl_u_rom_enable equ &b900 txt_set_paper equ &bb96 txt_clear_window equ &bb6c ;; encodings of the pixels (equivalent to SCR INK ENCODE would give us for mode 0) ;; values for left and right pixel (only 2 pixels per byte in mode 0) pen0_r equ &00 pen1_r equ &40 pen2_r equ &04 pen3_r equ &44 pen4_r equ &10 pen5_r equ &50 pen6_r equ &14 pen7_r equ &54 pen8_r equ &01 pen9_r equ &41 pen10_r equ &05 pen11_r equ &45 pen12_r equ &11 pen13_r equ &51 pen14_r equ &15 pen15_r equ &55 pen0_l equ pen0_r*2 pen1_l equ pen1_r*2 pen2_l equ pen2_r*2 pen3_l equ pen3_r*2 pen4_l equ pen4_r*2 pen5_l equ pen5_r*2 pen6_l equ pen6_r*2 pen7_l equ pen7_r*2 pen8_l equ pen8_r*2 pen9_l equ pen9_r*2 pen10_l equ pen10_r*2 pen11_l equ pen11_r*2 pen12_l equ pen12_r*2 pen13_l equ pen13_r*2 pen14_l equ pen14_r*2 pen15_l equ pen15_r*2 org &4000 ;; uncomment to see that this causes an effect ;;call kl_u_rom_enable ;; set mode 0 xor a call scr_set_mode ;; set paper ld a,1 call txt_set_paper ;; clears window to paper colour call txt_clear_window ;; plot point ;; ;; for mode 0: x is in the range 0-159 ;; for mode 1: x is in the range 0-320 ;; for mode 2: x is in the range 0-639 ;; for all modes: y is in the range 0-200 ;; origin is bottom left ;; get address of pixel ;; change coords for mode 1 and 2 to get same location as mode 0 ld de,80 ;; x ld hl,100 ;; y call scr_dot_position ;; HL = address of byte containing pixel ;; C = bit mask for pixel ;; B = number of pixels in byte push hl push bc ld a,3 ;; pen 3 ;; lookup encoded pixels from array ;; this performs a similar thing to SCR INK ENCODE but ;; is fixed for mode 0 ;; a different array would be needed for mode 1 ld l,a ld h,0 ld de,inks add hl,de ;; HL = address in array ld a,(hl) ;; A = pen 3 encoded into a form to poke to screen ;; but which would set all pixels in that byte pop bc pop hl ;; isolate just the pixel we want ;; using the pixel mask and c ld d,a ;; this avoids SCR PIXELS, but it is more complex. ;; We also require screen memory to be readable and writeable. ;; e.g. upper rom can't be enabled. ;; ;; SCR PIXELS does all the work necessary to enable/disable rom. ;; ;; ;; we need to read from screen ;; mask the pixels we don't want to change ;; combine with our pixel and write back ;; mask for pixel we want to write ld a,c ;; complement it to make mask for pixels to keep cpl ;; isolate pixels on screen and (hl) ;; combine with our pixel or d ;; write to screen ld (hl),a ret inks: defb pen0_l+pen0_r defb pen1_l+pen1_r defb pen2_l+pen2_r defb pen3_l+pen3_r defb pen4_l+pen4_r defb pen5_l+pen5_r defb pen6_l+pen6_r defb pen7_l+pen7_r defb pen8_l+pen8_r defb pen9_l+pen9_r defb pen10_l+pen10_r defb pen11_l+pen11_r defb pen12_l+pen12_r defb pen13_l+pen13_r defb pen14_l+pen14_r defb pen15_l+pen15_r