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##################################################################

# TITLE: Boot Up Code

# AUTHOR: Steve Rhoads (rhoadss@yahoo.com)

# DATE CREATED: 1/12/02

# FILENAME: boot.asm

# PROJECT: MIPS 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

   ori   $sp,$0,0x8000     #initialize stack pointer

   ori   $4,$0,1

   mtc0  $4,$12            #STATUS=1; enable interrupts

        jal     main2

   nop

$L1:

   j $L1

   nop

   nop

isr_storage:        #address 0x20

   nop

   nop

   nop

   nop

   #address 0x30

interrupt_service_routine:

   sw $4,-4($sp)

   sw $5,-8($sp)

   ori $5,$0,0xffff

   ori $4,$0,46

   sb $4,0($5)      #echo out '.'

   lw $5,-8($sp)

   #normally clear the interrupt source here

   #re-enable interrupts

   ori $4,$0,0x1

   mtc0 $4,$12      #STATUS=1; enable interrupts

   #FIXME there is a small race condition here!

   mfc0 $4,$14      #C0_EPC=14

   j $4

   lw $4,-4($sp)

   .set reorder

        .end    entry