mcs-51并行口的扩展

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1、第七章MCS-51并行口的扩展MCS51单片机内部有4个并行口，当内部并行口不够用时可以外扩并行口芯片。可外扩的并行口芯片很多，分成2类：不可编程的并行口芯片（74LS3734和74LS245）和可编程的并行口芯片（8255）。7.1不可编程并行口芯片的扩展7.2可编程并行口芯片的扩展7.1.174LS373的扩展7.1.274LS245的扩展7.1不可编程并行口芯片的扩展1、74LS373的结构2、74LS373的引脚3、74LS373与89C51的连接7.1.174LS373的扩展连接图DCPQDCPQDCPQDCPQDCPQDCPQDCPQDCPQD0D1D

2、2D3D4D5D6D7Q0Q1QQ3Q4Q5Q6Q7LEOE思考ALERDWRPSENP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.789C51P2.0P2.1P2.2P2.3P2.4P2.5P2.6P2.7A0A1A2A3A4A5A6A7OELED0D1D2D3D4D5D6D774LS373DBABCBOE～D0D774LS373～AB15AB0AB15地址码的计算LE74LS373与89C51的连接图+Q7Q6Q5Q4Q3Q2Q1Q0计算74LS373的地址（8051送出何种地址码时可以将数送到Q端）P27P26P25P24P23P22P21P

3、20P07P06P05P04P03P02P01P00AB15AB14AB13AB12AB11AB10AB9AB8AB7AB6AB5AB4AB3AB2AB1AB00***************ALERDWRPSENP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.789C51P2.0P2.1P2.2P2.3P2.4P2.5P2.6P2.7A0A1A2A3A4A5A6A7OELED0D1D2D3D4D5D6D774LS373DBABCBOE～D0D774LS373～AB15AB0AB15LE思考:2片74LS373与89C51的连接图+Q7Q6Q5Q4Q

4、3Q2Q1Q0OE～D0D774LS373～LE+Q7Q6Q5Q4Q3Q2Q1Q0计算74LS373的地址（8051送出何种地址码时可以将数送到Q端）P27P26P25P24P23P22P21P20P07P06P05P04P03P02P01P00AB15AB14AB13AB12AB11AB10AB9AB8AB7AB6AB5AB4AB3AB2AB1AB001**************10**************AB141、74LS245的结构2、74LS245的引脚3、74LS245与89C51的连接7.1.274LS245的扩展连接图B0A0思考B1A1B2

5、A2B3A3B4A4B5A5B6A6B7A7++EDIRALERDWRPSENP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.789C51P2.0P2.1P2.2P2.3P2.4P2.5P2.6P2.7A0A1A2A3A4A5A6A7OELED0D1D2D3D4D5D6D774LS373DBABCBDIR～B0B774LS245～AB15AB0AB15地址码的计算E74LS245与89C51的连接图+A7A6A5A4A3A2A1A0计算74LS245的地址（8051送出何种地址码时可以将数由A端传到B端）P27P26P25P24P23P22P21P2

6、0P07P06P05P04P03P02P01P00AB15AB14AB13AB12AB11AB10AB9AB8AB7AB6AB5AB4AB3AB2AB1AB00***************ALERDWRPSENP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.789C51P2.0P2.1P2.2P2.3P2.4P2.5P2.6P2.7A0A1A2A3A4A5A6A7OELED0D1D2D3D4D5D6D774LS373DBABCBDIR～B0B774LS245～AB15AB0AB15E思考:2片74LS245与89C51的连接图+A7A6A5A4A3

7、A2A1A0DIR～B0B774LS245～E+A7A6A5A4A3A2A1A0计算74LS245的地址P27P26P25P24P23P22P21P20P07P06P05P04P03P02P01P00AB15AB14AB13AB12AB11AB10AB9AB8AB7AB6AB5AB4AB3AB2AB1AB001**************10**************AB147.2.18255的结构7.2.28255的引脚7.2.38255的工作方式7.2.48255的控制字7.2.58255的应用7.2可编程并行口芯片的扩展（8255）8255有三个并行的8位

8、I/O接口