单片机C语言入门.ppt

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1、输入/输出口的高级应用第五章7/29/20211例說89S51-C語言89S51-C语言本章内容4x4键盘的内部结构TackSwitch的结构由TackSwitch所构成的4×4键盘连接上拉电阻4x4键盘市售一体成型的4x4键盘低电平扫描－按下“0”键低电平动作键盘动作分析表X3X2X1X0Y3Y2Y1Y0动作按键11101110Key01101Key11011Key20111Key311011110Key41101Key51011Key60111Key710111110Key81101Key91

2、011KeyA0111KeyB01111110KeyC1101KeyD1011KeyE0111KeyFxxxx1111无按键按下高电平扫描－按下“0”键高电平动作键盘动作分析表X3X2X1X0Y3Y2Y1Y0动作按键00010001Key00010Key10100Key21000Key300100001Key40010Key50100Key61000Key701000001Key80010Key90100KeyA1000KeyB10000001KeyC0010KeyD0100KeyE1000Key

3、Fxxxx0000无按键按下4×4键盘扫描电路A~f编码表数字(dp)gfedcba16进制显示a101000000xa0b100000110x83c101001110xa7d101000010xa1e100001000x84f100011100x8e程序-1程序-2键盘扫描IC数据传输模式-1数据传输模式-2MM74C922/MM74C923编码表按键连接引脚DataEDataDDataCDataBDataA0X0/Y0000001X1/Y0000012X2/Y0000103X3/Y000011

4、4X0/Y1001005X1/Y1001016X2/Y1001107X3/Y1001118X0/Y2010009X1/Y20100110X2/Y20101011X3/Y20101112X0/Y30110013X1/Y30110114X2/Y30111015X3/Y30111116X0/Y41000017X1/Y41000118X2/Y41001019X3/Y410011四个共阳极七段LED数码管四位数七段LED数码管模块(左为正面图、右为背面图)市售四位数七段LED数码管模块市售四位数七段LED数

5、码管模块七段LED数码管模块七段LED数码管模块设计技巧四位数的扫描：可使用50到100Ω的限流电阻，其瞬间电流将限制在66到33mA。若整个扫描周期为16ms，每位数约4ms点亮。因此，平均电流约为16.5mA到8.3mA。八位数的扫描：可使用25到50Ω的限流电阻，其瞬间电流将限制在132到66mA。若整个扫描周期为16ms，每位数约2ms点亮。因此，平均电流约为16.5mA到8.3mA。7446、7447、7448、7449的引脚7446、7447、7448真值表数字或功能输入7446/74

6、477448输出输出DCBAabcdefgabcdefg011000010000001111111011x000111001111011000021x001010010010110110131x001110000110111100141x010011001100011001151x010110100100101101161x011011100000001111171x011110001111111000081x100010000000111111191x1001100011001110011101

7、x1010111100100001101111x1011111001100011001121x1100110111000100011131x1101101101001001011141x1110111100000001111151x1111111111110000000BIxxxxxx011111110000000RBI100000011111110000000LT0xxxxx10000000111111174LS49真值表数字或功能输入输出DCBABIabcdefg000001111111010

8、0011011000020010111011013001111111001401001011001150101110110116011010011111701111111000081000111111119100111110011101010100011011110111001100112110010100011131101110010111411101000111115111110000000BIxxxx00000000七段LED数码管应用范例7446、7447、7448、74L