8051液晶的'Hello World' - 可变取代DB [英] 8051 LCD 'Hello World' - replacing DB with variable

问题描述

我使用的是专有的8051板学习汇编编程。我目前工作的一个LCD的'Hello World程序上。这里的code。

I'm using a proprietary 8051 board to learn assembly programming. I'm currently working on an LCD 'Hello World' program. Here's the code.

lcd_cmd equ 0800h           ;Write COMMAND reg address 0800h
lcd_st  equ 0801h           ;Read STATUS reg address 0801h
lcd_wr  equ 0802h           ;Write DATA reg address 0802h
lcd_rd  equ 0803h           ;Read DATA reg address 0803h

ORG 08100h

hello:  
mov P2, #(lcd_cmd SHR 8)            ;load P2 with high address
mov R0, #(lcd_cmd AND 255)          ;load R0 with command reg addr
mov R7, #03h                        ;set LCD position, line=1, char=3
mov dptr, #mesg1                    ;point to mesg1
acall   wr_string                   ;write mesg1 to LCD

mov R7, #41h                        ;set LCD position, line= 2, char=1
mov dptr, #mesg2                    ;point to mesg2
acall   wr_string                   ;write mesg2 to LCD

stop:   ajmp    stop                ;soft halt  

wr_string:
acall   lcd_busy        ;wait until LCD not busy
mov a, R7                           ;get LCD position
orl a, #080h                        ;msb set for LCD RAM address
movx    @R0, a                      ;write lcd_cmd to set line & char
nxt_char:
acall   lcd_busy                    ;wait until LCD not busy
clr a
movc    a, @a+dptr          
inc dptr                            ;point to next byte in string
jz  str_end                         ;if 0 then end of string

mov R1, #(lcd_wr AND 255)           ;Load R1 with wr_data address
movx    @R1, a                      ;Write char to LCD
sjmp    nxt_char                    ;get next char in string
str_end:    ret

lcd_busy:
mov R1, #(lcd_st AND 255)       ;Load R1 with status address
movx    a, @R1                          ;read LCD status
jb  acc.7, lcd_busy         ;keep checking until busy bit clear
ret

mesg1:  db  "Hello   ",0
mesg2:  db  "World ",0
END

一切工作正常。然而，我无法输出到LCD的变量。更换＃mesg1用十六进制值（ASCII让事情变得简单）简单地调出屏幕上的乱码。所以不调用子程序这只是增加每次价值，所以我不能确定时，它的移动到DPTR应该是什么格式的数据。

Everything works fine. However, I'm having trouble outputting a variable to the LCD. Replacing #mesg1 with a hex value (ascii to keep things simple) simply brings up scrambled characters on the screen. So does calling a subroutine which simply increments a value every time, so I'm unsure what format the data should be when it's moved into the dptr.

任何愚蠢的事我已经错过了？

Anything stupid I've missed?

谢谢！

推荐答案

DPTR 包含文本的地址显示。所以，如果你替换＃mesg1 的东西，如

dptr contains the address of the text to display. So, if you replace #mesg1 with something like

mov dptr, #045h

你在地址×45，这也解释了您看到乱码输出从内存（随机）内容。

you are outputting the (random) contents from memory at address 0x45, which explains the scrambled characters you see.

为了输出部分十进制值，则需要先将其转换成ASCII字符串，那么你可以使用现有的 wr_string 程序来把它打印出来。见的http://www.electro-tech-online.com/microcontrollers/14371-hex-decimal-then-ascii.html为code样品（I，J，K包含结果字符串，你仍然需要为您的日常wr_string零终止）。

In order to output some decimal value, you need to convert it to an ascii string first, then you can use your existing wr_string routine to get it printed. See http://www.electro-tech-online.com/microcontrollers/14371-hex-decimal-then-ascii.html for a code sample (i,j,k contains the result string which you still need to zero-terminate for your wr_string routine).

以下code显示了类似的程序。
需要注意的是 wr_string 需要修改读取XDATA数据，而不是从code内存（ MOVX A，@dptr 而不是 CLR A / MOVC A，@ A + DPTR ）

The following code shows a similar routine. Note that wr_string needs to be modified to read the data from XDATA, not from code memory (movx a, @dptr instead of clr a / movc a, @a+dptr):

    ORG     08100h

hello:
    mov     r7, #42        ; value to convert
    mov     dptr, #buffer  ; destination buffer
    acall   str2ascii      ; convert value

    mov     P2, #(lcd_cmd SHR 8)   ; load P2 with high address
    mov     R0, #(lcd_cmd AND 255) ; load R0 with command reg addr
    mov     R7, #03h        ; set LCD position, line=1, char=3
    mov     dptr, #buffer   ; point to buffer
    acall   wr_string       ; write buffer to LCD

...

str2ascii:
; Converts a one byte decimal value into its ASCII string representation.
; Result is prepended with leading zeroes.
; 0   becomes "000"
; 42  becomes "042"
; 255 becomes "255"
;
; @param r7    Input value to convert (1 byte, 0 .. 255)
; @param dptr  Destination buffer, at 4 bytes (3 digits plus \0)
;
    mov     a, r7
    mov     b, #100
    div     ab        ; leftmost digit in a
    add     a,#30h    ; convert to ASCII
    movx    @dptr, a
    inc     dptr

    mov     a,b       ; get reminder
    mov     b,#10
    div     ab        ; middle digit in a, rightmost digit in b
    add     a,#30h    ; convert to ASCII
    movx    @dptr, a
    inc     dptr

    mov     a,b
    add     a,#30h    ; convert to ASCII
    movx    @dptr,a
    inc     dptr

    mov     a,#0
    movx    @dptr, a  ; terminate string
    ret

    xseg
buffer:     ds 17     ; one LCD line plus terminating \0

    end

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