[英]Push Button on 68K
I want to Write a program to read a value from the push buttons and display that value on the LEDs. 我想编写一个程序来从按钮中读取一个值并在LED上显示该值。 The program should run continuously and as the push buttons are changed, the display changes. 该程序应连续运行,并且随着按钮的改变,显示也会改变。 I tried many ways but it does not show any thing in Could any one help me to know where is the problem. 我尝试了很多方法,但是它没有显示任何内容。有人可以帮助我知道问题出在哪里。
LEDS EQU $E00010 ;LEDS adress
BUTTON EQU $E00014 ;BUTTON address
ORG $400 ;start of program area
START
Loop MOVE.B #2,D0
MOVE.B BUTTON,D1 ;move the value of button to D1
MOVE.B D2,LEDS
NOT.B D1 ;take NOT to flip the value in order to present it in LEDS
MOVE.B D1,D2 ;move the value to LEDS
SUB.B #2,D0 ; if D0 =0 then loop again
BEQ Loop
SIMHALT
END START
A few things are missing from this. 一些缺少的东西。
A button is normally a single bit, not a whole byte, so there should be some form of mask applied to the button input. 按钮通常是单个位,而不是整个字节,因此应在按钮输入上应用某种形式的掩码。 Similarly setting an LED normally involves setting a single bit, not a byte, unless it is some form of multicolor LED. 同样,设置LED通常涉及设置一位而不是字节,除非它是某种形式的多色LED。 I am assuming you have 8 push buttons and 8 corresponding LEDs 我假设您有8个按钮和8个相应的LED
The code you have illustrated will run continuously because you load D0 with 2 after the LOOP label, and at the end of the loop you subtract 2 from D0 (which has the value 2) and then loop if that result is equal to zero ie always. 您说明的代码将连续运行,因为在LOOP标签后将D2装入2,然后在循环结束时从D0中减去2(其值为2),如果结果等于零,则循环,即始终。 If you really want a continuous loop, there is no point in using D0 at all. 如果您确实想要连续循环,则根本没有必要使用D0。
LEDS EQU $E00010 ;LEDS address BUTTON EQU $E00014 ;BUTTON address ORG $400 ;start of program area START LOOP MOVE.B BUTTON,D1 ; Read buttons NOT.B D1 ; LEDs are inverse of button MOVE.B D1,LEDS ; write to LEDs BRA.S LOOP ; do continously SIMHALT ; doesn't get here but still END START
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