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display.s
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display.s
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/*
* Dragon - Display setup
* Copyright (C) 2016 Sandor Zsuga (Jubatian)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "m74cfg.h"
#include <avr/io.h>
; (Needed only for register names for X, Y and Z)
.section .text
/*
** Sets up a display mode along with a reset address, and halts execution (so
** after generating a frame with the new mode, it returns onto that reset
** address). The reset address must be specified as a progmem address
** (converting a function pointer to int is OK for this).
**
** r24: Mode to set up (see define values in header)
** r23:r22: Reset address
*/
.global display_set
display_set:
; Common initialization
push r24
sts m74_reset + 0, r22
sts m74_reset + 1, r23
ldi r24, 34 ; Display start offset at line 34
ldi r22, 196 ; Display height is 196 pixels
call SetRenderingParameters
ldi r22, lo8(LOC_TDESC_OFF)
ldi r23, hi8(LOC_TDESC_OFF)
sts m74_tdesc + 0, r22
sts m74_tdesc + 1, r23
ldi r24, 56 ; RAM tiles used for sprites
sts m74_rtmax, r24
ldi XL, lo8(M74_ROWS_OFF)
ldi XH, hi8(M74_ROWS_OFF)
ldi r24, 0xFF
ldi r25, 27 * 3
st X+, r24
dec r25
brne .-6 ; Clear all 27 row selectors
pop r24
; Branch off to mode specific inits
cpi r24, 1
brcs mode_game ; 0: DISPLAY_GAME
breq mode_story ; 1: DISPLAY_STORY
; 2: DISPLAY_INTRO
; Intro screens are thinner
ldi r24, 34 + 24
ldi r22, 196 - 48
call SetRenderingParameters
ldi r22, lo8(LOC_TDESC_OFF)
ldi r23, hi8(LOC_TDESC_OFF)
; Set up palettes
ldi r21, 0x00 ; Black & White top palette, sky bits zero
; Initialize row selectors
ldi XL, lo8(M74_ROWS_OFF)
ldi XH, hi8(M74_ROWS_OFF)
ldi r25, 0
ldi r24, 19 * 8
st X+, r24
st X+, r25 ; 10 + 1 text rows beginning with row 19
ldi ZL, 80
ldi r24, 248 + 4
st X+, ZL
st X+, r24
st X+, r25 ; Separator with palette replace on end
ldi ZL, 84
st X+, ZL
st X+, r25
st X+, r25 ; 8 tile rows
; The rest is same as story mode
rjmp mode_story_com
mode_game:
; Set up palettes
ldi r21, 0x10 ; Yellow & Red top palette, sky bits zero
; Initialize row selectors
ldi XL, lo8(M74_ROWS_OFF)
ldi XH, hi8(M74_ROWS_OFF)
ldi r25, 0
ldi r24, 48 + 192 + 9
st X+, r24
st X+, r25 ; Top padding (2 separators)
ldi r24, 2
st X+, r24
ldi r24, 48 + 192
st X+, r24
st X+, r25 ; Status row
ldi r24, 10
st X+, r24
ldi r24, 48 + 192 + 15
st X+, r24
st X+, r25 ; Single separator with palette change
ldi r24, 11
st X+, r24
ldi r24, 48
st X+, r24
st X+, r25 ; Initial graphics screen
; Set up tile row descriptor source
ldi ZL, lo8(RES_SCR_GAME_OFF)
ldi ZH, hi8(RES_SCR_GAME_OFF)
; Set up tile row address source
ldi r24, lo8(RES_TID_GAME_OFF)
ldi r25, hi8(RES_TID_GAME_OFF)
rjmp mode_end
mode_story:
; Set up palettes
ldi r21, 0x10 ; Yellow & Red top palette, sky bits zero
; Initialize row selectors
ldi XL, lo8(M74_ROWS_OFF)
ldi XH, hi8(M74_ROWS_OFF)
ldi r25, 0
ldi r24, 248 + 1
st X+, r24
st X+, r25 ; Top padding (2 separators)
ldi r24, 2
st X+, r24
ldi r24, (12 + 16) * 8
st X+, r24
st X+, r25 ; Top frame row
ldi ZL, 10
ldi r24, (12 + 18) * 8
st X+, ZL
st X+, r24
st X+, r25
subi ZL, 0xF8
cpi ZL, 34
brne .-12 ; 3 empty rows
ldi r24, (12 ) * 8
st X+, ZL
st X+, r24
st X+, r25 ; 16 text rows
ldi ZL, 162
ldi r24, (12 + 18) * 8
st X+, ZL
st X+, r24
st X+, r25
subi ZL, 0xF8
cpi ZL, 186
brne .-12 ; 3 empty rows
st X+, ZL
ldi r24, (12 + 17) * 8
st X+, r24
st X+, r25 ; Bottom frame row
ldi r24, 194
st X+, r24
ldi r24, 248 + 1
st X+, r24
st X+, r25 ; Bottom padding (2 separators)
mode_story_com:
; Set up tile row descriptor source
ldi ZL, lo8(RES_SCR_STORY_OFF)
ldi ZH, hi8(RES_SCR_STORY_OFF)
; Set up tile row address source
ldi r24, lo8(RES_TID_STORY_OFF)
ldi r25, hi8(RES_TID_STORY_OFF)
mode_end:
; Write palette select
lds r20, global_palsel
andi r20, 0x0F ; Keep sky selection
or r20, r21 ; Add other palette settings
sts global_palsel, r20
; Write tile row address
sts m74_tidx + 0, r24
sts m74_tidx + 1, r25
; Write tile row descriptors
movw XL, r22 ; LOC_TDESC_OFF
ldi r25, 32
lpm r24, Z+
st X+, r24
dec r25
brne .-8
; Finalize: enable M74, halt to wait for reset
ldi r24, 0x9A ; 0x08: M74_CFG_RAM_PALETTE
; 0x02: M74_CFG_RAM_TDESC
; 0x10: M74_CFG_COL0_RELOAD
; 0x80: M74_CFG_ENABLE
sts m74_config, r24
rjmp .-2 ; Wait for M74 reset
/*
** Clears VRAM for a given display mode
**
** r24: Mode to clear for (see define values in header)
*/
.global display_clear
display_clear:
ldi XL, lo8(M74_VRAM_OFF)
ldi XH, hi8(M74_VRAM_OFF)
ldi r23, 0x7F ; Blank tile (black)
cpi r24, 1
brcs cl_game ; 0: DISPLAY_GAME
breq cl_story ; 1: DISPLAY_STORY
; 2: DISPLAY_INTRO
ldi r24, lo8(M74_VRAM_OFF + ( 8 * 25))
ldi r25, hi8(M74_VRAM_OFF + ( 8 * 25))
rcall cl_crut
ldi XL, lo8(LOC_INTXTVRAM_OFF)
ldi XH, hi8(LOC_INTXTVRAM_OFF)
ldi r24, lo8(LOC_INTXTVRAM_OFF + (11 * 32))
ldi r25, hi8(LOC_INTXTVRAM_OFF + (11 * 32))
ldi r23, 0x60 ; Blank tile (space)
rjmp cl_crut
cl_game:
ldi r24, lo8(M74_VRAM_OFF + (24 * 25))
ldi r25, hi8(M74_VRAM_OFF + (24 * 25))
rcall cl_crut
ldi r24, lo8(M74_VRAM_OFF + (24 * 25) + 32)
ldi r25, hi8(M74_VRAM_OFF + (24 * 25) + 32)
ldi r23, 0x20 ; Blank tile (space)
cl_crut:
st X+, r23 ; Small clear routine
cp XL, r24
cpc XH, r25
brne .-8
ret
cl_story:
ldi r24, lo8(M74_VRAM_OFF + (19 * 32))
ldi r25, hi8(M74_VRAM_OFF + (19 * 32))
ldi r23, 0x60 ; Blank tile (space)
rcall cl_crut
; Add story borders
ldi XL, lo8(M74_VRAM_OFF + (16 * 32))
ldi XH, hi8(M74_VRAM_OFF + (16 * 32))
ldi r24, lo8(M74_VRAM_OFF + (16 * 32) + 32)
ldi r25, hi8(M74_VRAM_OFF + (16 * 32) + 32)
ldi r23, 0x41
rcall cl_crut
ldi r24, lo8(M74_VRAM_OFF + (17 * 32) + 32)
ldi r25, hi8(M74_VRAM_OFF + (17 * 32) + 32)
ldi r23, 0x46
rcall cl_crut
ldi r23, 0x40
sts (M74_VRAM_OFF + (16 * 32) + 0), r23
ldi r23, 0x42
sts (M74_VRAM_OFF + (16 * 32) + 31), r23
ldi r23, 0x45
sts (M74_VRAM_OFF + (17 * 32) + 0), r23
ldi r23, 0x47
sts (M74_VRAM_OFF + (17 * 32) + 31), r23
ldi XL, lo8(M74_VRAM_OFF + 0)
ldi XH, hi8(M74_VRAM_OFF + 0)
ldi r24, lo8(M74_VRAM_OFF + 0 + (16 * 32))
ldi r25, hi8(M74_VRAM_OFF + 0 + (16 * 32))
ldi r23, 0x43
sts (M74_VRAM_OFF + (18 * 32) + 0), r23
rcall cl_crutvb
ldi XL, lo8(M74_VRAM_OFF + 31)
ldi XH, hi8(M74_VRAM_OFF + 31)
ldi r24, lo8(M74_VRAM_OFF + 31 + (16 * 32))
ldi r25, hi8(M74_VRAM_OFF + 31 + (16 * 32))
ldi r23, 0x44
sts (M74_VRAM_OFF + (18 * 32) + 31), r23
cl_crutvb:
st X+, r23 ; Small routine for vertical borders
adiw XL, 31
cp XL, r24
cpc XH, r25
brne .-10
ret