# *** Startup Code (executed after Reset) ***
# Standard definitions of Mode bits and Interrupt (I & F) flags in PSRs
.equ Mode_USR, 0x1F
.equ Mode_FIQ, 0x11
.equ Mode_IRQ, 0x12
.equ Mode_SVC, 0x13
.equ Mode_ABT, 0x17
.equ Mode_UND, 0x1B
.equ Mode_SYS, 0x1F
.equ I_Bit, 0x80 /* when I bit is set, is disabled */
.equ F_Bit, 0x40 /* when F bit is set, FIQ is disabled */
/*
// <h> Stack Configuration
// <o> Top of Stack Address <0x0-0xFFFFFFFF>
// <h> Stack Sizes (in Bytes)
// <o1> Undefined Mode <0x0-0xFFFFFFFF>
// <o2> Supervisor Mode <0x0-0xFFFFFFFF>
// <o3> Abort Mode <0x0-0xFFFFFFFF>
// <o4> Fast Interrupt Mode <0x0-0xFFFFFFFF>
// <o5> Interrupt Mode <0x0-0xFFFFFFFF>
// <o6> User/System Mode <0x0-0xFFFFFFFF>
// </h>
// </h>
*/
.equ Top_Stack, 0x40004000
.equ UND_Stack_Size, 0x00000004
.equ SVC_Stack_Size, 0x00000400
.equ ABT_Stack_Size, 0x00000004
.equ FIQ_Stack_Size, 0x00000004
.equ IRQ_Stack_Size, 0x00000080
.equ USR_Stack_Size, 0x00000400
.equ SYS_Stack_Size, 0x00000020
# Phase Locked Loop (PLL) definitions
.equ PLL_BASE, 0xE01FC080 /* PLL Base Address */
.equ PLLCON_OFS, 0x00 /* PLL Control Offset*/
.equ PLLCFG_OFS, 0x04 /* PLL Configuration Offset */
.equ PLLSTAT_OFS, 0x08 /* PLL Status Offset */
.equ PLLFEED_OFS, 0x0C /* PLL Feed Offset */
.equ PLLCON_PLLE, (1<<0) /* PLL Enable */
.equ PLLCON_PLLC, (1<<1) /* PLL Connect */
.equ PLLCFG_MSEL, (0x1F<<0) /* PLL Multiplier */
.equ PLLCFG_PSEL, (0x03<<5) /* PLL Divider */
.equ PLLSTAT_PLOCK, (1<<10) /* PLL Lock Status */
/*
// <e> PLL Setup
// <o1.0..4> MSEL: PLL Multiplier Selection
// <1-32><#-1>
// <i> M Value
// <o1.5..6> PSEL: PLL Divider Selection
// <0=> 1 <1=> 2 <2=> 4 <3=> 8
// <i> P Value
// </e>
*/
.equ PLL_SETUP, 1
.equ PLLCFG_Val, 0x00000024
# Memory Accelerator Module (MAM) definitions
.equ MAM_BASE, 0xE01FC000 /* MAM Base Address */
.equ MAMCR_OFS, 0x00 /* MAM Control Offset*/
.equ MAMTIM_OFS, 0x04 /* MAM Timing Offset */
/*
// <e> MAM Setup
// <o1.0..1> MAM Control
// <0=> Disabled
// <1=> Partially Enabled
// <2=> Fully Enabled
// <i> Mode
// <o2.0..2> MAM Timing
// <0=> Reserved <1=> 1 <2=> 2 <3=> 3
// <4=> 4 <5=> 5 <6=> 6 <7=> 7
// <i> Fetch Cycles
// </e>
*/
.equ MAM_SETUP, 1
.equ MAMCR_Val, 0x00000002
.equ MAMTIM_Val, 0x00000004
# Starupt Code must be linked first at Address at which it expects to run.
.text
.arm
.global _startup
.func _startup
_startup:
# Exception Vectors
# Mapped to Address 0.
# Absolute addressing mode must be used.
# Dummy Handlers are implemented as infinite loops which can be modified.
Vectors: LDR PC, Reset_Addr
LDR PC, Undef_Addr
LDR PC, SWI_Addr
LDR PC, PAbt_Addr
LDR PC, DAbt_Addr
NOP /* Reserved Vector */
LDR PC, IRQ_Addr
LDR PC, FIQ_Addr
Reset_Addr: .word Reset_Handler
Undef_Addr: .word Undef_Handler
SWI_Addr: .word SWI_Handler
PAbt_Addr: .word PAbt_Handler
DAbt_Addr: .word DAbt_Handler
.word 0 /* Reserved Address */
IRQ_Addr: .word IRQ_Handler
FIQ_Addr: .word FIQ_Handler
Undef_Handler: B Undef_Handler
SWI_Handler: B SWI_Handler
PAbt_Handler: B PAbt_Handler
DAbt_Handler: B DAbt_Handler
IRQ_Handler: B IRQ_Handler
FIQ_Handler: B FIQ_Handler
# Reset Handler
Reset_Handler:
.if PLL_SETUP
LDR R0, =PLL_BASE
MOV R1, #0xAA
MOV R2, #0x55
# Configure and Enable PLL
MOV R3, #PLLCFG_Val
STR R3, [R0, #PLLCFG_OFS]
MOV R3, #PLLCON_PLLE
STR R3, [R0, #PLLCON_OFS]
STR R1, [R0, #PLLFEED_OFS]
STR R2, [R0, #PLLFEED_OFS]
# Wait until PLL Locked
PLL_Loop: LDR R3, [R0, #PLLSTAT_OFS]
ANDS R3, R3, #PLLSTAT_PLOCK
BEQ PLL_Loop
# Switch to PLL Clock
MOV R3, #(PLLCON_PLLE | PLLCON_PLLC)
STR R3, [R0, #PLLCON_OFS]
STR R1, [R0, #PLLFEED_OFS]
STR R2, [R0, #PLLFEED_OFS]
.endif
.if MAM_SETUP
LDR R0, =MAM_BASE
MOV R1, #MAMTIM_Val
STR R1, [R0, #MAMTIM_OFS]
MOV R1, #MAMCR_Val
STR R1, [R0, #MAMCR_OFS]
.endif
# Initialise Interrupt System
#..
# Setup Stack for each mode
LDR R0, =Top_Stack
# Enter Undefined Instruction Mode and set its Stack Pointer
MSR CPSR_c, #Mode_UND|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #UND_Stack_Size
# Enter Abort Mode and set its Stack Pointer
MSR CPSR_c, #Mode_ABT|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #ABT_Stack_Size
# Enter FIQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_FIQ|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #FIQ_Stack_Size
# Enter IRQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_IRQ|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #IRQ_Stack_Size
# Enter Supervisor Mode and set its Stack Pointer
MSR CPSR_c, #Mode_SVC|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #SVC_Stack_Size
# Enter User Mode and set its Stack Pointer
MSR CPSR_c, #Mode_USR|I_Bit|F_Bit
MOV SP, R0
# Setup a default Stack Limit (when compiled with "-mapcs-stack-check")
SUB SL, SP, #USR_Stack_Size
# Relocate .data section (Copy from ROM to RAM)
LDR R1, =_etext
LDR R2, =_data
LDR R3, =_edata
LoopRel: CMP R2, R3
LDRLO R0, [R1], #4
STRLO R0, [R2], #4
BLO LoopRel
# Clear .bss section (Zero init)
MOV R0, #0
LDR R1, =__bss_start__
LDR R2, =__bss_end__
LoopZI: CMP R1, R2
STRLO R0, [R1], #4
BLO LoopZI
# Enter the C code
ADR LR, __main_exit
LDR R0, =main
BX R0
__main_exit: B __main_exit
.size _startup, . - _startup
.endfunc
.end
