Steward

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掌機 - PMP V - Assembly - UART

---

main.s

    .equiv zero,      $0
    .equiv at,        $1
    .equiv v0,        $2
    .equiv v1,        $3
    .equiv a0,        $4
    .equiv a1,        $5
    .equiv a2,        $6
    .equiv a3,        $7
    .equiv t0,        $8
    .equiv t1,        $9
    .equiv t2,        $10
    .equiv t3,        $11
    .equiv t4,        $12
    .equiv t5,        $13
    .equiv t6,        $14
    .equiv t7,        $15
    .equiv s0,        $16
    .equiv s1,        $17
    .equiv s2,        $18
    .equiv s3,        $19
    .equiv s4,        $20
    .equiv s5,        $21
    .equiv s6,        $22
    .equiv s7,        $23
    .equiv t8,        $24
    .equiv t9,        $25
    .equiv k0,        $26
    .equiv k1,        $27
    .equiv gp,        $28
    .equiv sp,        $29
    .equiv fp,        $30
    .equiv ra,        $31

    .equiv CLKGR,     0xb0000020
    .equiv URBR0,     0xb0030000
    .equiv UDLLR0,    0xb0030000
    .equiv UDLHR0,    0xb0030004
    .equiv UIER0,     0xb0030004
    .equiv UFCR0,     0xb0030008
    .equiv ULCR0,     0xb003000c
    .equiv ULSR0,     0xb0030014
    .equiv ISR0,      0xb0030020
    .equiv PCFUNS,    0xb0010244
    .equiv PCTRGC,    0xb0010278
    .equiv PCSELS,    0xb0010254

    .globl _start
    .set noreorder
    .text
.ifdef STAGE2
    .word 0x555555ff
    .word 0x55555555
    .byte 0xff
    .byte 0xff
    .byte 0xff
    .byte 0x00
.endif
_start:
    nop
    li v0, 0x00400004 # disable interrupt
    mtc0 v0, $12
    li v1, 0x00800000 # clear cause content
    mtc0 v1, $13
    li sp, 0x80004000

uart_init:
    li v0, 0x1000
    sw v0, PCFUNS
    sw v0, PCTRGC
    sw v0, PCSELS
    lw v0, CLKGR
    li v1, 0xfffffffe
    and v0, v1
    sw v0, CLKGR
    sb zero, UIER0
    li v0, 0xef
    sb v0, UFCR0
    li v0, 0xfc
    sb v0, ISR0
    li v0, 0x03
    sb v0, ULCR0
    lbu v0, ULCR0
    ori v0, 0x80
    sb v0, ULCR0
    sb zero, UDLHR0
    li v0, 0x0d
    sb v0, UDLLR0
    lbu v0, ULCR0
    li v1, 0x7f
    and v0, v1
    sb v0, ULCR0
    li v0, 0x17
    sb v0, UFCR0
    jal delay
    li a0, 100
    jal uart_char
    li a0, 'A'
end:
    b end

uart_char:
    sb a0, URBR0
0:
    lbu v0, ULSR0
    andi v0, 0x60
    li v1, 0x60
    bne v0, v1, 0b
    nop
    jr ra
    nop

delay:
    li v0, 180
    mul a0, v0
0:
    bnez a0, 0b
    addiu a0, -1
    jr ra
    nop

main.ld

OUTPUT_ARCH(mips)
ENTRY(_start)

MEMORY
{
    low8k  : ORIGIN = 0x80000000 , LENGTH = 0x2000
    high8k : ORIGIN = 0x80002000 , LENGTH = 0x2000
}

SECTIONS
{
    .text : {
        *(.text.1)
        *(.text.0)
    } > low8k

    .data : {
        . = ALIGN(4);
        *(.rodata*) *(.data*) *(.scommon*) *(.reginfo*)
    } > low8k

    .bss : {
        . = ALIGN(4);
        _bss_start = ABSOLUTE(.);
        *(.sbss*) *(.bss*)
        . = ALIGN(4);
        _bss_end = ABSOLUTE(.);
    } > high8k

    __stack = 0x80004000;
}

Makefile

all:
	mipsel-linux-as -o main.o main.s --defsym=STAGE1=1
	mipsel-linux-ld -T main.ld -o main.elf main.o
	mipsel-linux-objcopy -O binary main.elf stage1.bin

clean:
	rm -rf main.o main.elf main.bin stage1.bin

編譯

$ cd
$ wget https://github.com/steward-fu/website/releases/download/pmp-v/bin_rs90-toolchain-2019.04.30.tar
$ tar xvf bin_rs90-toolchain-2019.04.30.tar
$ sudo mv rs90-toolchain /opt/
$ export PATH=$PATH:/opt/rs90-toolchain/usr/bin
$ make

接著進入燒錄模式(按下B插入USB)，再使用jzboot燒錄stage1.bin就可以