129 lines
1.9 KiB
ArmAsm
129 lines
1.9 KiB
ArmAsm
.text
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.global _start
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_start:
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ldr r0, =0x7000cffc // stack_start
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mov sp, r0
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mov r2, #0xffffffff
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ldr r1, =0x7000c000 // stack_end
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clear_stack:
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cmp r1, r0
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str r2, [r0]
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sub r0, r0, #4
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bcc clear_stack
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bl wdt_disable
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clear_psram:
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mov r0, #0
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mov r1, #0x00800000
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mov r2, #0
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clear_psram_loop:
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cmp r1, r0
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str r2, [r0], #4
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bcc clear_psram_loop
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print_welcome_banner:
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adr r0, welcome_banner
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bl uart_puts
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load_program:
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bl uart_getc
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mov r5, r0
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lsls r5, r5, #0
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mov r4, r5
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bl uart_getc
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mov r5, r0
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lsls r5, r5, #8
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orr r4, r5
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bl uart_getc
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mov r5, r0
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lsls r5, r5, #16
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orr r4, r5
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bl uart_getc
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mov r5, r0
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lsls r5, r5, #24
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orr r4, r5
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# r4 now contains the number of bytes to load.
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# r5 contains the current offset to write to.
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# Load bytes from the serial port into RAM.
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mov r5, #0
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loader_loop:
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bl uart_getc
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strb r0, [r5], #1
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sub r4, #1
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cmp r4, #0
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bne loader_loop
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jump_to_new_program:
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adr r0, launch_message
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bl uart_puts
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mov r0, #0
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mov pc, r0
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.align 4
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welcome_banner:
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.ascii "Fernvale bootloader\r\nWrite four bytes of program size, then\r\n"
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.asciz "write program data...\r\n>"
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launch_message:
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.asciz "Launching program...\r\n"
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.align 4
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uart_putc:
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stmfd sp!, {lr}
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ldr r2, =0xa0080014 // uart offset
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uart_putc_ready_wait:
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ldrb r1, [r2]
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tst r1, #0x20
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beq uart_putc_ready_wait
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sub r2, r2, #0x14
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strb r0, [r2]
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ldmfd sp!, {pc}
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uart_puts:
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stmfd sp!, {lr}
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mov r3, r0
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uart_puts_loop:
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ldrb r0, [r3], #1
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cmp r0, #0
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beq uart_exit
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bl uart_putc
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b uart_puts_loop
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uart_exit:
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ldmfd sp!, {pc}
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uart_getc:
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stmfd sp!, {lr}
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ldr r2, =0xa0080014 // uart offset
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uart_getc_ready_wait:
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ldrb r1, [r2]
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tst r1, #0x01
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beq uart_getc_ready_wait
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sub r2, r2, #0x14
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ldrb r0, [r2]
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ldmfd sp!, {pc}
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asm_memcpy:
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mov r3, r1
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add r3, r3, r2
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asm_memcpy_loop:
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cmp r1, r3
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ldrcc r2, [r1], #4
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strcc r2, [r0], #4
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bcc asm_memcpy_loop
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bx lr
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wdt_disable:
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ldr r1, =0xa0030000
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mov r0, #0x2200
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str r0, [r1]
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bx lr
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