mtboot.s

unix v7是最后一个广泛发布的研究型UNIX版本

/ tape boot program to load and transfer
/ the next item on the tape.

/ entry is made by jsr pc,*$0
/ so return can be rts pc

core = 24.
halt=0
.. = [core*2048.]-512.
start:
	mov	$..,sp
	mov	sp,r1
	cmp	pc,r1
	bhis	2f
	clr	r0
	cmp	(r0),$407
	bne	1f
	mov	$20,r0
1:
	mov	(r0)+,(r1)+
	cmp	r1,$core*2048.
	blo	1b
	jmp	(sp)

2:
	mov	$1f,*$4
	mov	$340,*$6
	tst	*$htcs1
	mov	$htrew,rew
	mov	$htread,tread
	br	2f
1:
	mov	$tmread,tread
	mov	$tmrew,rew
2:
	jsr	pc,*rew
	mov	$2,tapa
	mov	$-256.,wc
	jsr	pc,*tread

	mov	*$2,r0
	add	*$4,r0
	sub	$512.,r0
	asr	r0
	neg	r0
	bge	1f

	mov	r0,wc
	mov	$3,tapa
	mov	$512.,ba
	jsr	pc,*tread
1:
	jsr	pc,*rew
	clr	r0
	mov	$20,r1
	mov	sp,r4
	clc
	ror	r4
1:
	mov	(r1)+,(r0)+
	sob	r4,1b
	jsr	pc,*$0
	br	.

htcs1 = 172440
htba  = 172444
htfc  = 172446
htcs2 = 172450
htds  = 172452
httc  = 172472

P800 = 1300
P1600 = 2300
PIP = 20000
RESET = 40
MOL = 10000
ERR = 40000
REV = 33
READ = 71
REW = 7

htread:
1:
	mov	ba,mtma
	cmp	mtapa,tapa
	beq	1f
	bhi	2f
	jsr	pc,hrrec
	br	1b
2:
	jsr	pc,htrew
	br	1b
1:
	mov	wc,r1
1:
	jsr	pc,hrrec
	add	$256.,r1
	bmi	1b
	rts	pc

hrrec:
	mov	$htds,r0
	tstb	(r0)
	bpl	hrrec
	bit	$PIP,(r0)
	bne	hrrec
	bit	$MOL,(r0)
	beq	hrrec
	mov	$htfc,r0
	mov	$-512.,(r0)
	mov	mtma,-(r0)
	mov	$-256.,-(r0)
	mov	$READ,-(r0)
1:
	tstb	(r0)
	bpl	1b
	bit	$ERR,(r0)
	bpl	1f
	mov	$RESET,*$htcs2
	mov	$-1,*$htfc
	mov	$REV,(r0)
	br	hrrec
1:
	add	$512.,mtma
	inc	mtapa
	rts	pc

htrew:
	mov	$RESET,*$htcs2
	mov	$P800,*$httc
	mov	$REW,*$htcs1
	clr	mtapa
	rts	pc


mts = 172520
mtc = 172522
mtbrc = 172524
mtcma = 172526

tmread:
1:
	mov	ba,mtma
	cmp	mtapa,tapa
	beq	1f
	bhi	2f
	jsr	pc,tmrrec
	br	1b
2:
	jsr	pc,tmrew
	br	1b
1:
	mov	wc,r1
1:
	jsr	pc,tmrrec
	add	$256.,r1
	bmi	1b
	rts	pc

tmrrec:
	mov	$mts,r0
	bit	$2,(r0)+		/ rewind status
	bne	tmrrec
	tstb	(r0)+		/ cu ready
	bpl	tmrrec
	inc 	r0
	mov	$-512.,(r0)+	/ byte count
	mov	mtma,(r0)	/ bus address
	mov	$mtc,r0
	mov	$60003,(r0)		/ read 800bpi
1:
	tstb	(r0)
	bpl	1b
	tst	(r0)+
	bpl	1f
	mov	$-1,(r0)
	mov	$60013,-(r0)		/ backspace
	br	tmrrec
1:
	add	$512.,mtma
	inc	mtapa
	rts	pc

tmrew:
	mov	$60017,*$mtc
	clr	mtapa
	rts	pc

mtapa:	0
mtma:	0
tapa:	0
wc:	0
ba:	0
rew:	0
tread:	0