鸿 网 互 联 www.68idc.cn

關於汇编语言的問題解决办法

来源:互联网 作者:佚名 时间:2015-09-03 08:12
關於 汇编语言 的問題 這個是案鍵的編程式 但我有些部分看不懂 麻煩大大幫幫忙幫我解釋一下 謝謝 #include avr/io.h //function prototypes for user defined functions char ReadKeypad(); int main() { unsigned char key; DDRA = 0xFF; while(1) { key =
關於汇编语言的問題
這個是案鍵的編程式
但我有些部分看不懂
麻煩大大幫幫忙幫我解釋一下
謝謝
#include   <avr/io.h>

//function   prototypes   for   user   defined   functions
char   ReadKeypad();

int   main()
{
unsigned   char   key;

DDRA   =   0xFF;

while(1)
{
key   =   ReadKeypad();

if   (key==0xFF)   continue;     //不懂

PORTA   =   key;                       //不懂
}

while(1);
return   0;
}

//define   a   look-up   table
char   lookup[]={   '1 ',   '2 ',   '3 ',   'A ',
'4 ',   '5 ',   '6 ',   'B ',
'7 ',   '8 ',   '9 ',   'C ',
'* ',   '0 ',   '# ',   'D '};

char   ReadKeypad()
{
//declare   local   variables
unsigned   char   row,   col;
unsigned   char   input,   shift;

//define   Port   D   to   connect   to   the   kaypad
//PD0   -   PD3   as   input,   PD4   -   PD7   as   output
DDRD   =   0xF0;         //不懂     為什麼是0xF0   而不是0xFF

//write   1 's   to   those   pins   defined   as   input
//to   enable   the   pull-up   R 's
PORTD   =   0xFF;

//prepare   scanning
row   =   0; //the   first   row         //不懂
shift   =   0x10; //the   first   row   as   1         //不懂

//start   scanning
for   (row=0;   row <4;   row++)
{
PORTD   =   ~shift;                 //不懂
shift   =   shift < <1; //shift   < <=   1;         //不懂
input   =   PIND;                                 //不懂

input   =   input   |   0xF0; //screen   the   output   pins   //不懂
input   =   ~(input);       //不懂

if   (input   !=   0)           //不懂
break;

}

//any   key   pressed?
if   (row   <   4)           //不懂
{
//the   loop   was   broken   because   a   key   was   pressed
//the   row   output   0   is   the   row   value

//find   out   the   col   which   is   1
shift   =   0x01;       //不懂
for   (col=0;   col <4;   col++)       //不懂
{
if   (input   &   shift)     //不懂
{
//use   input   to   hold   the   key   value
input   =   4*row   +   col;     //不懂
//return   input;
return   lookup[input];       //不懂
}
shift   =   shift < <1;       //不懂
}
网友评论
<