Subversion Repositories eco32

;
; start.s -- startup code
;
 
	.import	main
	.import	task0StkTop
	.import	currentStkTop
	.import	_ecode
	.import	_edata
	.import	_ebss
 
	.export	_bcode
	.export	_bdata
	.export	_bbss
 
	.export	enable
	.export	disable
	.export	orMask
	.export	andMask
	.export	getISR
	.export	setISR
	.export	startTask
	.export	setTLB
 
	.code
_bcode:
 
	.data
_bdata:
 
	.bss
_bbss:
 
	.code
 
	; reset arrives here
reset:
	j	start
 
	; interrupts arrive here
intrpt:
	j	isr
 
	; user TLB misses arrive here
userMiss:
	j	isr
 
isr:
	add	$26,$29,$0		; sp -> $26
	add	$27,$1,$0		; $1 -> $27
	ldw	$29,$0,currentStkTop	; setup kernel mode stack
	sub	$29,$29,128		; save registers
	stw	$2,$29,8
	stw	$3,$29,12
	stw	$4,$29,16
	stw	$5,$29,20
	stw	$6,$29,24
	stw	$7,$29,28
	stw	$8,$29,32
	stw	$9,$29,36
	stw	$10,$29,40
	stw	$11,$29,44
	stw	$12,$29,48
	stw	$13,$29,52
	stw	$14,$29,56
	stw	$15,$29,60
	stw	$16,$29,64
	stw	$17,$29,68
	stw	$18,$29,72
	stw	$19,$29,76
	stw	$20,$29,80
	stw	$21,$29,84
	stw	$22,$29,88
	stw	$23,$29,92
	stw	$24,$29,96
	stw	$25,$29,100
	stw	$26,$29,116		; this is the task's sp
	stw	$27,$29,4		; this is the task's $1
	stw	$30,$29,120		; this is the task's resumption addr
	stw	$31,$29,124
	add	$5,$29,$0		; $5 = pointer to register array
	mvfs	$4,0			; $4 = IRQ number
	slr	$4,$4,16
	and	$4,$4,0x1F
	sll	$26,$4,2		; $26 = 4 * IRQ number
	ldw	$26,$26,irqsrv		; get addr of service routine
	jalr	$26			; call service routine
	j	resume			; resume task if ISR returns
 
	; resume a task
resume:
	ldw	$29,$0,currentStkTop	; setup kernel mode stack
	sub	$29,$29,128		; restore registers
	ldw	$2,$29,8
	ldw	$3,$29,12
	ldw	$4,$29,16
	ldw	$5,$29,20
	ldw	$6,$29,24
	ldw	$7,$29,28
	ldw	$8,$29,32
	ldw	$9,$29,36
	ldw	$10,$29,40
	ldw	$11,$29,44
	ldw	$12,$29,48
	ldw	$13,$29,52
	ldw	$14,$29,56
	ldw	$15,$29,60
	ldw	$16,$29,64
	ldw	$17,$29,68
	ldw	$18,$29,72
	ldw	$19,$29,76
	ldw	$20,$29,80
	ldw	$21,$29,84
	ldw	$22,$29,88
	ldw	$23,$29,92
	ldw	$24,$29,96
	ldw	$25,$29,100
	ldw	$26,$29,116		; this is the task's sp
	ldw	$27,$29,4		; this is the task's $1
	ldw	$30,$29,120		; this is the task's resumption addr
	ldw	$31,$29,124
	add	$1,$27,$0		; $27 -> $1
	add	$29,$26,$0		; $26 -> sp
	rfx				; return from exception
 
start:
	mvfs	$8,0
	or	$8,$8,1 << 27		; let vector point to RAM
	mvts	$8,0
	add	$10,$0,_bdata		; copy data segment
	add	$8,$0,_edata
	sub	$9,$8,$10
	add	$9,$9,_ecode
	j	cpytest
cpyloop:
	ldw	$11,$9,0
	stw	$11,$8,0
cpytest:
	sub	$8,$8,4
	sub	$9,$9,4
	bgeu	$8,$10,cpyloop
	add	$8,$0,_bbss		; clear bss
	add	$9,$0,_ebss
	j	clrtest
clrloop:
	stw	$0,$8,0
	add	$8,$8,4
clrtest:
	bltu	$8,$9,clrloop
	ldw	$29,$0,task0StkTop	; setup kernel mode stack for task 0
	jal	main			; call 'main'
start1:
	j	start1			; loop
 
enable:
	mvfs	$8,0
	or	$8,$8,1 << 23
	mvts	$8,0
	jr	$31
 
disable:
	mvfs	$8,0
	and	$8,$8,~(1 << 23)
	mvts	$8,0
	jr	$31
 
orMask:
	mvfs	$8,0
	and	$4,$4,0x0000FFFF	; use lower 16 bits only
	or	$8,$8,$4
	mvts	$8,0
	jr	$31
 
andMask:
	mvfs	$8,0
	or	$4,$4,0xFFFF0000	; use lower 16 bits only
	and	$8,$8,$4
	mvts	$8,0
	jr	$31
 
getISR:
	sll	$4,$4,2
	ldw	$2,$4,irqsrv
	jr	$31
 
setISR:
	sll	$4,$4,2
	stw	$5,$4,irqsrv
	jr	$31
 
startTask:
	ldw	$29,$0,currentStkTop	; setup kernel mode stack
	sub	$29,$29,128
	stw	$0,$29,0		; preset registers
	stw	$0,$29,4
	stw	$0,$29,8
	stw	$0,$29,12
	stw	$0,$29,16
	stw	$0,$29,20
	stw	$0,$29,24
	stw	$0,$29,28
	stw	$0,$29,32
	stw	$0,$29,36
	stw	$0,$29,40
	stw	$0,$29,44
	stw	$0,$29,48
	stw	$0,$29,52
	stw	$0,$29,56
	stw	$0,$29,60
	stw	$0,$29,64
	stw	$0,$29,68
	stw	$0,$29,72
	stw	$0,$29,76
	stw	$0,$29,80
	stw	$0,$29,84
	stw	$0,$29,88
	stw	$0,$29,92
	stw	$0,$29,96
	stw	$0,$29,100
	stw	$0,$29,104
	stw	$0,$29,108
	stw	$0,$29,112
	add	$8,$0,0x80000000
	stw	$8,$29,116		; sp
	stw	$0,$29,120		; task starts at virtual addr 0
	stw	$0,$29,124
	mvfs	$8,0
	or	$8,$8,1 << 25		; set previous mode to 'user'
	or	$8,$8,1 << 22		; and enable interrupts
	mvts	$8,0
	j	resume
 
setTLB:
	mvts	$4,1			; set index
	mvts	$5,2			; set entryHi
	mvts	$6,3			; set entryLo
	tbwi				; write TLB entry at index
	jr	$31
 
	.data
 
; interrupt service routine table
 
	.align	4
 
irqsrv:
	.word	0		; 00: terminal 0 transmitter interrupt
	.word	0		; 01: terminal 0 receiver interrupt
	.word	0		; 02: terminal 1 transmitter interrupt
	.word	0		; 03: terminal 1 receiver interrupt
	.word	0		; 04: keyboard interrupt
	.word	0		; 05: unused
	.word	0		; 06: unused
	.word	0		; 07: unused
	.word	0		; 08: disk interrupt
	.word	0		; 09: unused
	.word	0		; 10: unused
	.word	0		; 11: unused
	.word	0		; 12: unused
	.word	0		; 13: unused
	.word	0		; 14: timer 0 interrupt
	.word	0		; 15: timer 1 interrupt
	.word	0		; 16: bus timeout exception
	.word	0		; 17: illegal instruction exception
	.word	0		; 18: privileged instruction exception
	.word	0		; 19: divide instruction exception
	.word	0		; 20: trap instruction exception
	.word	0		; 21: TLB miss exception
	.word	0		; 22: TLB write exception
	.word	0		; 23: TLB invalid exception
	.word	0		; 24: illegal address exception
	.word	0		; 25: privileged address exception
	.word	0		; 26: unused
	.word	0		; 27: unused
	.word	0		; 28: unused
	.word	0		; 29: unused
	.word	0		; 30: unused
	.word	0		; 31: unused