如何在循环中使用WriteHexByte显示到屏幕上？ [英] how do I display to the screen using writeHexByte in a loop?

问题描述

我在启动时显示了displayChar字符。现在如何添加WriteHexBytes，然后在循环中使用WriteHexByte和WriteHexWord将其显示在屏幕上。

*WriteHexByte 需要8位寄存器 通过调用 ConvertHexNibble和使用 WriteChar

*WriteHexWord 需要16位寄存器或内存 参数，并显示每个字节 通过调用WriteHexByte

因此，在编写字符之后，它需要显示宏WriteChar实现的机器代码。并在循环中使用WriteHexBytes进行显示

尝试的代码

 # Macro definition
.macro convertHexNibble register
    cmpb $10, 
egister
    jl 1f
    # process here is >=10
    add $0x37, 
egister
    jmp 2f  
    # process here is <=10
    1:
    add $0x30, 
egister    
    2:
    # expect the register to now be the ascii code
.endm

#.macro writeHexByte register
#convert
#.endm

.macro displayChar character color
mov $0x09, %ah
mov character, %al  
mov $0x00, %bh 
mov color, %bl 
mov $0x01, %cx
int $0x10
.endm

#set defualts values to move cursor off screen
.macro moveCursor row = $0xff column = $0xff
mov $0x02, %ah # ah = 02h moves the cursor row 2 col 2
mov $0x00, %bh # bh = 0 page
mov $0x02, %dh 
mov $0x02, %dl # dl=1
int $0x10
.endm

.macro sumArray array number result

# assume array is an array of bytes
#therefore the accumulator is just %al (8bits)
      mov $
umber, %cx  # AX will serve as a counter for 
                     # the number of words left to be summed 
      mov $0, %ax  # BX will store the sum
      mov array, %bx  # CX will point to the current 
                     # element to be summed
top:  add (%bx), %cx
      inc %bx  # move pointer to next element
      dec %ax  # decrement counter
      jnz top  # if counter not 0, then loop again
done: mov %ax, 
esult  # done, store result in "array"

.endm

# The main boot processing code
.code16
.text
.global _start
_start:

mov $06, %al
convertHexNibble %al
displayChar %al, $0xe3
moveCursor %ah
mov $0x0A, %al
convertHexNibble %al
displayChar %al, $0xe3

sumArray $x 4 sum

# writtenHexWord $sum

# move Cursor off screen invisble
moveCursor

cli # clear interrupts
hlt
x: .byte 1, 5, 2, 10    
#   char x[] = {1, 5, 2, 10};      
sum: .byte 0
# char sum = 0;

. = _start + 510
.byte 0x55
.byte 0xAA

推荐答案

WriteHexByte预期8位寄存器通过调用ConvertHexNibble并使用WriteChar来显示它

WriteHexWord需要16位寄存器或内存参数，并通过调用WriteHexByte显示每个字节

由于过度使用宏的，代码变得臃肿。每次调用宏时，在参数展开后，它的整个代码都会插入到调用发生的位置。使用宏的大部分操作应该使用子例程来完成。更短更快的程序！

尽管如此，我还是会向您展示一个基于您当前宏的解决方案。

• 必须通过对BIOS.Teleype函数0x0E的API调用来扩展displayChar宏，以便不会在相同的光标位置打印连续字符。
• 已通过先按0x30进行加法来优化ConvertHexNibble宏。这两种情况都必须发生，不是吗？

.macro displayChar character color
    mov  $0x01, %cx
    mov  $0x00, %bh 
    mov  color, %bl 
    mov  $0x09, %ah         # BIOS.WriteColoredCharacter
    mov  character, %al  
    int  $0x10
    mov  $0x0E, %ah         # BIOS.Teletype
    int  $0x10
.endm

.macro convertHexNibble register
    add  $0x30, 
egister    
    cmpb $0x39, 
egister
    jbe  1f
    # process here is >=10
    add  $0x07, 
egister
    1:
    # expect the register to now be the ascii code
.endm

.macro writeHexByte register
    mov  
egister, %al
    push %ax
    shr  $4, %al
    convertHexNibble %al
    displayChar %al, $0xE3
    pop  %ax
    and  $15, %al
    convertHexNibble %al
    displayChar %al, $0xE3
.endm

.macro writeHexWord register
    mov  
egister, %ax
    push %ax
    writeHexByte %ah
    pop  %ax
    writeHexByte %al
.endm

---

这是您的sum Array宏的更正版本，它真的、真的不应该作为宏存在！！

如果您注释"；#假定数组是字节数组"；，则何时将字添加到%cx中的当前总和？
而大多数其他评论甚至与代码不匹配。

.macro sumArray array number result
    # assume array is an array of bytes
    # therefore the accumulator is just %al (8bits)
      mov  $
umber, %cx
      mov  array, %bx
      xor  %ax, %ax
top:  add  (%bx), %al
      inc  %bx          # move pointer to next element
      dec  %cx          # decrement counter
      jnz  top          # if counter not 0, then loop again
      mov  %al, 
esult # (*)
.endm

(*)因为sum被定义为一个字节(sum: .byte 0)，所以您的最终存储永远不应写入%ax的完整单词。

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