按键扫描程序 ASM。1. 键盘采用4*5矩阵键盘,含有两个组合键.

2. 硬件连接比较混乱,且各个按键的排列与面贴上的键码对应混乱.如果采用教科书上常规矩阵键盘的

扫描方式实现比较繁琐.

3. 需要识别两个双键,但这两个双键位置比较特殊K17,K18和K19,K20.

4. 基于2,3两点.这里采用列,行分别输出全零,读取行,列的引脚电平信息.综合这两组信息查表获取键值.

对于单键按下,有两个位为0.对于两个按键按下,有3或4个位为0.

-Key scanner ASM. 1. Keyboard with 4* 5 matrix keyboard, with two key combination.　2. Hardware connection is a bit confusing, and the arrangement of the various buttons and paste the key code corresponding to face chaos. If the use of conventional textbooks matrix keyboard　scanning more complicated to achieve.　3. need to identify the two double bonds, but the two double bonds are special positions K17, K18 and K19, K20.　4. Based on 2,3 points. here with columns, rows are all zero output , read the rows, columns of pin-level information. comprehensive information look-up table for the two sets of keys.　For Speed Press, there are two bits to 0. For the two buttons pressed, 3 or 4 bit to 0.