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[/] [plasma/] [tags/] [V2_1/] [tools/] [boot.asm] - Rev 47
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##################################################################
# TITLE: Boot Up Code
# AUTHOR: Steve Rhoads (rhoadss@yahoo.com)
# DATE CREATED: 1/12/02
# FILENAME: boot.asm
# PROJECT: Plasma CPU core
# COPYRIGHT: Software placed into the public domain by the author.
# Software 'as is' without warranty. Author liable for nothing.
# DESCRIPTION:
# Initializes the stack pointer and jumps to main2().
##################################################################
.text
.align 2
.globl entry
.ent entry
entry:
.set noreorder
#These nine instructions must be the first instructions
#convert.exe will correctly initialize $gp
lui $gp,0
ori $gp,$gp,0
#convert.exe will set $4=.sbss_start $5=.bss_end
ori $4,$0,0
ori $5,$0,0
ori $sp,$0,0xfff0 #initialize stack pointer
$BSS_CLEAR:
sw $0,0($4)
slt $3,$4,$5
bnez $3,$BSS_CLEAR
addiu $4,$4,4
jal main2
nop
$L1:
j $L1
#address 0x30
interrupt_service_routine:
#registers $26 and $27 are reserved for the OS
ori $26,$0,0xffff
ori $27,$0,46
sb $27,0($26) #echo out '.'
#normally clear the interrupt source here
#return and re-enable interrupts
ori $26,$0,0x1
mfc0 $27,$14 #C0_EPC=14
jr $27
mtc0 $26,$12 #STATUS=1; enable interrupts
.set reorder
.end entry
###################################################
.globl isr_enable
.ent isr_enable
isr_enable:
.set noreorder
jr $31
mtc0 $4,$12 #STATUS=1; enable interrupts
.set reorder
.end isr_enable
###################################################
.globl putchar
.ent putchar
putchar:
.set noreorder
li $5,0xffff
#Uncomment to make each character on a seperate line
#The VHDL simulator buffers the lines
# sb $4,0($5)
# ori $4,$0,'\n'
jr $31
sb $4,0($5)
.set reorder
.end putchar
###################################################
.globl puts
.ent puts
puts:
.set noreorder
ori $5,$0,0xffff
PUTS1:
lb $6,0($4)
beqz $6,PUTS2
addiu $4,$4,1
b PUTS1
sb $6,0($5)
PUTS2:
jr $31
ori $2,$0,0
.set reorder
.end puts
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