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[/] [plasma/] [trunk/] [tools/] [boot.asm] - Rev 390
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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 main().
##################################################################
#Reserve 512 bytes for stack
.comm InitStack, 512
.text
.align 2
.global entry
.ent entry
entry:
.set noreorder
#These four instructions should be the first instructions.
#convert.exe previously initialized $gp, .sbss_start, .bss_end, $sp
la $gp, _gp #initialize global pointer
la $5, __bss_start #$5 = .sbss_start
la $4, _end #$2 = .bss_end
la $sp, InitStack+488 #initialize stack pointer
$BSS_CLEAR:
sw $0, 0($5)
slt $3, $5, $4
bnez $3, $BSS_CLEAR
addiu $5, $5, 4
jal main
nop
$L1:
j $L1
.end entry
###################################################
#address 0x3c
.global interrupt_service_routine
.ent interrupt_service_routine
interrupt_service_routine:
.set noreorder
.set noat
#Registers $26 and $27 are reserved for the OS
#Save all temporary registers
#Slots 0($29) through 12($29) reserved for saving a0-a3
addi $29, $29, -104 #adjust sp
sw $1, 16($29) #at
sw $2, 20($29) #v0
sw $3, 24($29) #v1
sw $4, 28($29) #a0
sw $5, 32($29) #a1
sw $6, 36($29) #a2
sw $7, 40($29) #a3
sw $8, 44($29) #t0
sw $9, 48($29) #t1
sw $10, 52($29) #t2
sw $11, 56($29) #t3
sw $12, 60($29) #t4
sw $13, 64($29) #t5
sw $14, 68($29) #t6
sw $15, 72($29) #t7
sw $24, 76($29) #t8
sw $25, 80($29) #t9
sw $31, 84($29) #lr
mfc0 $26, $14 #C0_EPC=14 (Exception PC)
addi $26, $26, -4 #Backup one opcode
sw $26, 88($29) #pc
mfhi $27
sw $27, 92($29) #hi
mflo $27
sw $27, 96($29) #lo
lui $6, 0x2000
lw $4, 0x20($6) #IRQ_STATUS
lw $6, 0x10($6) #IRQ_MASK
and $4, $4, $6
jal OS_InterruptServiceRoutine
addi $5, $29, 0
#Restore all temporary registers
lw $1, 16($29) #at
lw $2, 20($29) #v0
lw $3, 24($29) #v1
lw $4, 28($29) #a0
lw $5, 32($29) #a1
lw $6, 36($29) #a2
lw $7, 40($29) #a3
lw $8, 44($29) #t0
lw $9, 48($29) #t1
lw $10, 52($29) #t2
lw $11, 56($29) #t3
lw $12, 60($29) #t4
lw $13, 64($29) #t5
lw $14, 68($29) #t6
lw $15, 72($29) #t7
lw $24, 76($29) #t8
lw $25, 80($29) #t9
lw $31, 84($29) #lr
lw $26, 88($29) #pc
lw $27, 92($29) #hi
mthi $27
lw $27, 96($29) #lo
mtlo $27
addi $29, $29, 104 #adjust sp
isr_return:
ori $27, $0, 0x1 #re-enable interrupts
jr $26
mtc0 $27, $12 #STATUS=1; enable interrupts
.end interrupt_service_routine
.set at
###################################################
.global OS_AsmInterruptEnable
.ent OS_AsmInterruptEnable
OS_AsmInterruptEnable:
.set noreorder
mfc0 $2, $12
jr $31
mtc0 $4, $12 #STATUS=1; enable interrupts
#nop
.set reorder
.end OS_AsmInterruptEnable
###################################################
.global OS_AsmInterruptInit
.ent OS_AsmInterruptInit
OS_AsmInterruptInit:
.set noreorder
#Patch interrupt vector to 0x1000003c
la $5, OS_AsmPatchValue
lw $6, 0($5)
sw $6, 0x3c($0)
lw $6, 4($5)
sw $6, 0x40($0)
lw $6, 8($5)
sw $6, 0x44($0)
lw $6, 12($5)
jr $31
sw $6, 0x48($0)
OS_AsmPatchValue:
#Registers $26 and $27 are reserved for the OS
#Code to place at address 0x3c
lui $26, 0x1000
ori $26, $26, 0x3c
jr $26
nop
.set reorder
.end OS_AsmInterruptInit
###################################################
.global setjmp
.ent setjmp
setjmp:
.set noreorder
sw $16, 0($4) #s0
sw $17, 4($4) #s1
sw $18, 8($4) #s2
sw $19, 12($4) #s3
sw $20, 16($4) #s4
sw $21, 20($4) #s5
sw $22, 24($4) #s6
sw $23, 28($4) #s7
sw $30, 32($4) #s8
sw $28, 36($4) #gp
sw $29, 40($4) #sp
sw $31, 44($4) #lr
jr $31
ori $2, $0, 0
.set reorder
.end setjmp
###################################################
.global longjmp
.ent longjmp
longjmp:
.set noreorder
lw $16, 0($4) #s0
lw $17, 4($4) #s1
lw $18, 8($4) #s2
lw $19, 12($4) #s3
lw $20, 16($4) #s4
lw $21, 20($4) #s5
lw $22, 24($4) #s6
lw $23, 28($4) #s7
lw $30, 32($4) #s8
lw $28, 36($4) #gp
lw $29, 40($4) #sp
lw $31, 44($4) #lr
jr $31
ori $2, $5, 0
.set reorder
.end longjmp
###################################################
.global OS_AsmMult
.ent OS_AsmMult
OS_AsmMult:
.set noreorder
multu $4, $5
mflo $2
mfhi $4
jr $31
sw $4, 0($6)
.set reorder
.end OS_AsmMult
###################################################
.global OS_Syscall
.ent OS_Syscall
OS_Syscall:
.set noreorder
syscall 0
jr $31
nop
.set reorder
.end OS_Syscall
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