[Coco] silly assembler fun

[Kevin Diggs]

Hi,

	Here is a minimally entertaining little program to 
not-so-pseudo-randomly set pixels on the G1C (64x64x4) screen. The 
random number generator is the simple random algorithm adapted from the 
book "Inner Loops". I think it is more entertaining than most of what is 
on television. Though the new Always Bad Channel (aka ABC) series Lost 
seems ok.

	Anyone know if G1C can be used under OS-9? In other words, is there 
anyway for me to say "I'll set and control the graphic hardware. Trust 
Me." to the OS? From what I remember it (OS-9)only supports the 6k modes.

	I can probably provide an assembled audio file if anyone is interested 
(Linux only).

	I might be smart enough to write some games ... except for the sound. 
Anyone out there who knows how to do sound willing to teach the masses?

	Nick, any arrangement we could come to so I could get the source for 
the Pacman game? I could certainly learn alot from you! I don't 
understand why you don't try to sell this on EBay? Are you worried about 
copyrights?

					kevin

rdotg1c:
*		org $1eb		adjust to align on 2 page 							boundary
*vbuf		rmb 1024		buffer for g1c mode
vbuf		equ $600		address of basic graphic page 1
start		bsr sg1c
		sta $ffd6		clear hybrid speed mode
		ldd #vbuf
		lsra
		bsr svaddr
		bsr gclr
		bra mloop
stlen		equ .-start
*
gclr		ldx #vbuf
		leay 1024,x
		pshs y
clgtop		clr ,x+
		cmpx ,s
		bne clgtop
		leas 2,s
gcdone		rts
gclen		equ .-gclr
*
sg1c		ldx #$ff22
		lda ,x
		anda #7
		ora #$80
		sta ,x
		leax $9f,x		$ff22 + $9f = $ffc1 -> x
		sta ,x+
		sta ,x++
		sta ,x
sgdone		rts
sg1len		equ .-sg1c
*
sa		ldx $ff22
		lda ,x
		anda #7
		ora $8
		sta ,x
		leax $9e,x		$ff22 + $9e = $ffc0 -> x
		sta ,x++
		sta ,x++
		sta ,x
sadone		rts
salen		equ .-sa
*
svaddr		ldx $ffc6
		ldb #7
		pshs b
svtop		clrb
		lsra
		adcb #0
		sta b,x
		leax 2,x
		dec ,s
		bne svtop
		leas 1,s
svdone		rts
svalen		equ .-svaddr
*
mloop		nop
noise		leax seed,pcr
		pshs x
		lbsr simran
		leay prod,pcr
		puls x
		ldd ,x++
		std ,y
		ldd ,x
		std 2,y
		lda 3,y
		ldb 2,y
		stb 4,y
		ldb 1,y
		stb 3,y
		ldb ,y
		andb #$f
		stb 2,y
		sta 1,y
		lda ,y
		lsra
		lsra
		lsra
		lsra
		sta ,y
		ldd 2,y
		lsra
		rorb
		lsra
		rorb
		eora 3,y
		eorb 4,y
		lda 3,y
		anda #$3
		sta 3,y
		ldx #vbuf
		ldd 3,y
		leax d,x
		ldd ,y
		pshs a
		eorb ,s
		tfr b,a
		lsra
		lsra
		lsra
		lsra
		sta ,s
		eorb ,s
		andb #$f
		tfr b,a
		lsra
		lsra
		sta ,s
		lda #3
		andb #3
		beq pmok
pmsh		lsla
		lsla
		lsl ,s
		lsl ,s
		decb
		bne pmsh
pmok		coma
		anda ,x
		ora ,s+
		sta ,x
		jsr [$a000]
		beq noise
		cmpa #'q
		beq bye
		cmpa #'c
		bne chkr
		lda $ff22
		eora #$8
		sta $ff22
		lbra noise
chkr		cmpa #'r
		bne chkf
		lbsr gclr
		lbra noise
chkf		cmpa #'f
		bne chkn
		sta $ffd9
		lbra noise
chkn		cmpa #'n
		bne nexkey
		sta $ffd8
nexkey		lbra noise
bye		lbsr sa
		lda #2
		lbsr svaddr
		sta $ffd8
mldone		rts
mllen		equ .-mloop
*
simran		leay mcand,pcr
		leau prod,pcr
		bsr mul3x4
		leau prod,pcr
		leau 4,u
		ldx 2,s
		ldd ,u++
		std ,x++
		ldd ,u++
		std ,x++
		leay radd,pcr
		leay 4,y
		andcc #$fe
		ldb #4
addtop		lda ,-y
		adca ,-x
		sta ,x
		decb
		bne addtop
sidone		rts
simlen		equ .-simran
*
mul3x4		lda #8			clr dest
cltop		clr ,u+
		deca
		bne cltop
		leax 4,x		x points to byte above lsbyte
		leay 2,y		y ponts to lsbyte
		pshs u,x
		lda #3
		pshs a			outter loop count
otop		ldx 1,s
		ldu 3,s
		lda #4
		pshs a			inner loop count
itop		lda ,-x
		ldb ,y
		mul
		addb ,-u
		stb ,u
		adca -1,u
		sta -1,u
		bcc noc
		pshs u
		leau -1,u
ctop		inc ,-u			ripple carry
		beq ctop
		puls u
noc		dec ,s
		bne itop
		leas 1,s
		leay -1,y
		ldu 3,s
		leau -1,u
		stu 3,s
		dec ,s
		bne otop
		leas 5,s
mudone		rts
mulen		equ .-mul3x4
zclen		equ .-start
radd		fdb #3c6e
		fdb #f35f
seed		fdb $99
		fdb $99
mcand		fcb $19
		fcb $66
		fcb $0d
prod		rmb 8
zdlen		equ .-radd
		end