First I will start with posting the actual startup.s code from 'Hello Jag users!
Thanks to VladR for this. Reprinted with permission.
Code: Select all
.include "jaguar.inc"
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; Begin STARTUP PICTURE CONFIGURATION -- Edit this to change startup picture
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PPP .equ 8 ; Pixels per Phrase (1-bit)
BMP_WIDTH .equ 320 ; Width in Pixels
BMP_HEIGHT .equ 200 ; Height in Pixels
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; End of STARTUP PICTURE CONFIGURATION
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; Globals
.globl gSetOLP
.globl olp2set
.globl ticks
.globl a_vdb
.globl a_vde
.globl a_hdb
.globl a_hde
.globl width
.globl height
.globl _vidmem
; Externals
.extern ___main
.extern _SetPallete
BMP_PHRASES .equ (BMP_WIDTH/PPP) ; Width in Phrases
BMP_LINES .equ (BMP_HEIGHT*2) ; Height in Half Scanlines
BITMAP_OFF .equ (2*8) ; Two Phrases
LISTSIZE .equ 5 ; List length (in phrases)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; Program Entry Point Follows...
.text
move.l #$70007,G_END ; big-endian mode
move.l #$70007,D_END
move.w #$FFFF,VI ; disable video interrupts
move.l #INITSTACK,a7 ; Setup a stack
jsr InitVideo ; Setup our video registers.
jsr InitLister ; Initialize Object Display List
jsr InitVBint ; Initialize our VBLANK routine
;;; Sneaky trick to cause display to popup at first VB
move.l #$0,listbuf+BITMAP_OFF
move.l #$C,listbuf+BITMAP_OFF+4
move.l d0,olp2set ; D0 is swapped OLP from InitLister
move.l #gSetOLP,G_PC ; Set GPU PC
move.l #RISCGO,G_CTRL ; Go!
waitforset:
move.l G_CTRL,d0 ; Wait for write.
andi.l #$1,d0
bne waitforset
move.w #$6C7,VMODE ; Configure Video
jmp ___main ; Jump to main code
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Procedure: gSetOLP
; Use the GPU to set the OLP and quit.
;
; Inputs: olp2set - Variable contains pre-swapped value to stuff OLP with.
;
; NOTE!!!: This code can run in DRAM only because it contains no JUMP's or
; JR's. It will generate a warning with current versions of MADMAC
; because it doesn't '.ORG'.
;
.long
.gpu
gSetOLP:
movei #olp2set,r0 ; Read value to write
load (r0),r1
movei #OLP,r0 ; Store it
store r1,(r0)
moveq #0,r0 ; Stop GPU
movei #G_CTRL,r1
store r0,(r1)
nop ; Two "feet" on the brake pedal
nop
.68000
.bss
.long
olp2set: .ds.l 1 ; GPU Code Parameter
.text
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; Procedure: InitVBint
; Install our vertical blank handler and enable interrupts
;
InitVBint:
move.l d0,-(sp)
move.l #UpdateList,LEVEL0 ; Install 68K LEVEL0 handler
move.w a_vde,d0 ; Must be ODD
ori.w #1,d0
move.w d0,VI
move.w #C_VIDENA,INT1 ; Enable video interrupts
move.w sr,d0
and.w #$F8FF,d0 ; Lower 68k IPL to allow
move.w d0,sr ; interrupts
move.l (sp)+,d0
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Procedure: InitVideo (same as in vidinit.s)
; Build values for hdb, hde, vdb, and vde and store them.
;
InitVideo:
movem.l d0-d6,-(sp)
move.w CONFIG,d0 ; Also is joystick register
andi.w #VIDTYPE,d0 ; 0 = PAL, 1 = NTSC
beq palvals
move.w #NTSC_HMID,d2
move.w #NTSC_WIDTH,d0
move.w #NTSC_VMID,d6
move.w #NTSC_HEIGHT,d4
bra calc_vals
palvals:
move.w #PAL_HMID,d2
move.w #PAL_WIDTH,d0
move.w #PAL_VMID,d6
move.w #PAL_HEIGHT,d4
calc_vals:
move.w d0,width
move.w d4,height
move.w d0,d1
asr #1,d1 ; Width/2
sub.w d1,d2 ; Mid - Width/2
add.w #4,d2 ; (Mid - Width/2)+4
sub.w #1,d1 ; Width/2 - 1
ori.w #$400,d1 ; (Width/2 - 1)|$400
move.w d1,a_hde
move.w d1,HDE
move.w d2,a_hdb
move.w d2,HDB1
move.w d2,HDB2
move.w d6,d5
sub.w d4,d5
move.w d5,a_vdb
add.w d4,d6
move.w d6,a_vde
move.w a_vdb,VDB
move.w #$FFFF,VDE
move.l #0,BORD1 ; Black border
move.w #0,BG ; Init line buffer to black
movem.l (sp)+,d0-d6
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; InitLister: Initialize Object List Processor List
;
; Returns: Pre-word-swapped address of current object list in d0.l
;
; Registers: d0.l/d1.l - Phrase being built
; d2.l/d3.l - Link address overlays
; d4.l - Work register
; a0.l - Roving object list pointer
InitLister:
movem.l d1-d4/a0,-(sp) ; Save registers
lea listbuf,a0
move.l a0,d2 ; Copy
add.l #(LISTSIZE-1)*8,d2 ; Address of STOP object
move.l d2,d3 ; Copy for low half
lsr.l #8,d2 ; Shift high half into place
lsr.l #3,d2
swap d3 ; Place low half correctly
clr.w d3
lsl.l #5,d3
; Write first BRANCH object (branch if YPOS > a_vde )
clr.l d0
move.l #(BRANCHOBJ|O_BRLT),d1 ; $4000 = VC < YPOS
or.l d2,d0 ; Do LINK overlay
or.l d3,d1
move.w a_vde,d4 ; for YPOS
lsl.w #3,d4 ; Make it bits 13-3
or.w d4,d1
move.l d0,(a0)+
move.l d1,(a0)+
; Write second branch object (branch if YPOS < a_vdb)
; Note: LINK address is the same so preserve it
andi.l #$FF000007,d1 ; Mask off CC and YPOS
ori.l #O_BRGT,d1 ; $8000 = VC > YPOS
move.w a_vdb,d4 ; for YPOS
lsl.w #3,d4 ; Make it bits 13-3
or.w d4,d1
move.l d0,(a0)+
move.l d1,(a0)+
; Write a standard BITMAP object
move.l d2,d0
move.l d3,d1
ori.l #BMP_HEIGHT<<14,d1 ; Height of image
move.w height,d4 ; Center bitmap vertically
sub.w #BMP_HEIGHT,d4
add.w a_vdb,d4
andi.w #$FFFE,d4 ; Must be even
lsl.w #3,d4
or.w d4,d1 ; Stuff YPOS in low phrase
move.l #_vidmem,d4
lsl.l #8,d4
or.l d4,d0
move.l d0,(a0)+
move.l d1,(a0)+
movem.l d0-d1,bmpupdate
; Second Phrase of Bitmap
move.l #BMP_PHRASES>>4,d0 ; Only part of top LONG is IWIDTH
move.l #O_DEPTH8|O_NOGAP,d1 ; Bit Depth = 16-bit, Contiguous data
move.w width,d4 ; Get width in clocks
lsr.w #2,d4 ; /4 Pixel Divisor
sub.w #BMP_WIDTH,d4
lsr.w #1,d4
or.w d4,d1
ori.l #(BMP_PHRASES<<18)|(BMP_PHRASES<<28),d1 ; DWIDTH|IWIDTH
move.l d0,(a0)+
move.l d1,(a0)+
; Write a STOP object at end of list
clr.l (a0)+
move.l #(STOPOBJ|O_STOPINTS),(a0)+
; Now return swapped list pointer in D0
move.l #listbuf,d0
swap d0
movem.l (sp)+,d1-d4/a0
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Procedure: UpdateList
; Handle Video Interrupt and update object list fields
; destroyed by the object processor.
UpdateList:
move.l a0,-(sp)
move.l #listbuf+BITMAP_OFF,a0
move.l bmpupdate,(a0) ; Phrase = d1.l/d0.l
move.l bmpupdate+4,4(a0)
add.l #1,ticks ; Increment ticks semaphore
move.w #$101,INT1 ; Signal we're done
move.w #$0,INT2
move.l (sp)+,a0
rte
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.data
.phrase
.bss
.dphrase
listbuf: .ds.l LISTSIZE*2 ; Object List
bmpupdate: .ds.l 2 ; One Phrase of Bitmap for Refresh
ticks: .ds.l 1 ; Incrementing # of ticks
a_hdb: .ds.w 1
a_hde: .ds.w 1
a_vdb: .ds.w 1
a_vde: .ds.w 1
width: .ds.w 1
height: .ds.w 1
_vidmem:
.ds.b 64000
vidend:
.end
VladR wrote:I spent some time in Assembler, going over the initialization of the video mode and object processor in file startup.s.
I finally forced myself to crosscheck the docs against several of the registers used in initialization of the video mode, as I mentioned last week that I'd like to do some experiments with the CRY mode (soon-ish), which required breaking down some constants (hence postponing for later).
In the statup.s, in the section waitforoffset, there is this line:That is not helpful. At all.Code: Select all
move.w #$6C7,VMODE ; Configure Video:
VMODE is register F00028 (described in detail in docs page 12)
The value $6C7 (hex) is 0000 0110 1100 0111 (binary)
Checking against JAGUAR.H, the above value can be rewritten as:Now that is infinitely mode readable as $6C7. Here's the description copied from the docs:VIDEN | CSYNC | BGEN | RGB16 | PWIDTH4Of interest are the bits for MODE and PWIDTH. Checking JAGUAR.H reveals the following for MODE:bit 0: VIDEN: Enable Video Interrupts
bit 6: CSYNC: Enables composite sync on the vertical sync output
bit 7: BGEN: Clears the line buffer to the colour in the background register after displaying the contents. This only has effect in CRY and RGB16 modes
bits 1-3: MODE = 3 RGB16: 16-bit RGB. Each 32-bit entry in the line buffer is treated as two 16-bit RGB pixels
bits 9-11: PWIDTH =3 PWIDTH4: This field determines the width of pixels in video clock cycles. The width is one more than the value in this field.Changing RGB16 to CRY16 should change the video mode to CRY. Changing it to RGB24 should change it to 24-bit.Code: Select all
#define CRY16 0x0000 /* 16-bit CRY mode */ #define RGB24 0x0002 /* 24-bit RGB mode */ #define DIRECT16 0x0004 /* 16-bit Direct mode */ #define RGB16 0x0006 /* 16-bit RGB mode */
I suspect the OP would have to be instructed to use O_DEPTH16 instead of O_DEPTH8 (and maybe a pitch would have to be adjusted too) in its second phrase - but I'll leave that exercise for later, when I'll play with CRY mode, as I will for sure have to reread the section on Object processor's bitmap definitions.
Now, let's get back to bits of PWIDTH:From docs:Code: Select all
#define PWIDTH1 0x0000 /* Pixel Dividers */ #define PWIDTH2 0x0200 #define PWIDTH3 0x0400 #define PWIDTH4 0x0600 #define PWIDTH5 0x0800 #define PWIDTH6 0x0A00 #define PWIDTH7 0x0C00 #define PWIDTH8 0x0E00So, this is where the actual horizontal resolution is being set. This must be sync'ed with the contents of the second phrase for OP:PWIDTH: This field determines the width of pixels in video clock cycles. The width is one more than the value in this field.Backtracking the ASM code few pages above reveals that width = NTSC_WIDTH, which according to JAGUAR.H is 1409.Code: Select all
move.w width,d4 ; Get width in clocks lsr.w #2,d4 ; /4 Pixel Divisor
Hence the code above can be rewritten as equation: d4 = NTSC_WIDTH / (2 ^ 2) = 1409 / 4 = 352
As vertical resolutions are only few and between (240p vs 480i), the default startup.s creates the resolution 352x240.
Experimenting with different values for the divisor should result in different horizontal resolutions. This could be a useful feature for VRBasic.