1.1-6 单片机的外部引脚

单片机的外部引脚VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0GND40393837363534333231302928272625242322211234567891011121314151617181920VCC、GND(40、20)：电源引脚，接入单片机的工作电源接+5V接电源地0VP0.0~P0.7(39~32)：P0口引脚P1.0~P1.7(1~7)：P1口引脚P2.0~P2.7(21~27)：P2口引脚P3.0~P3.7(10~17)：P3口引脚每个并行IO均为8位为准双向口输入输出数据VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0RSTXTAL2GNDXTAL140393837363534333231302928272625242322211234567891011121314151617181920X2：片内振荡器的反相放大器的输入端；外部时钟发生器的输入端。X1：片内振荡器的反相放大器的输出端。在该引脚输入两个机器周期以上的高电平时，单片机复位。RST：复位信号输入端VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0RSTXTAL2GNDXTAL1PSEN40393837363534333231302928272625242322211234567891011121314151617181920访问外部ROM时，产生负脉冲信号作为外部程序存储器的片选信号。在访问外部ROM的每个机器周期内，产生两个负脉冲信号。在访问外部ROM的每个机器周期内，产生两个负脉冲信号。PSEN非：外部ROM读选通引脚VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0RSTXTAL2GNDXTAL1ALEPSEN40393837363534333231302928272625242322211234567891011121314151617181920ALE：地址锁存允许引脚单片机正常运行时，ALE以1/6晶振频率输出脉冲。该引脚为CPU访问外部存储器提供地址锁存信号，信号下降沿将低8位地址锁存到片外地址锁存器中。VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0EARSTXTAL2GNDXTAL1ALEPSEN40393837363534333231302928272625242322211234567891011121314151617181920EA非：外部ROM选择引脚当该引脚为高电平时，从片内ROM读取指令，只有当PC超出片内ROM地址范围时，才转到外部ROM中读取指令。当该引脚为低电平时，一律从外部ROM中读取指令。VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0EARSTXTAL2GNDXTAL1ALEPSEN/RXD/TXD/INT0/INT1/T0/T1/WR/RD40393837363534333231302928272625242322211234567891011121314151617181920RXD（P3.0）：串行数据输入端TXD（P3.1）：串行数据输出端INT0（P3.2）:外部中断0申请输入端INT1（P3.3）:外部中断1申请输入端VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0EARSTXTAL2GNDXTAL1ALEPSEN/RXD/TXD/INT0/INT1/T0/T1/WR/RD40393837363534333231302928272625242322211234567891011121314151617181920T0（P3.4）：计数器0外部计数脉冲输入端T1（P3.5）：计数器1外部计数脉冲输入端WR（P3.6）:写外设控制信号输出端RD（P3.7）:读外设控制信号输出端VccP0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7P3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7P2.7P2.6P2.5P2.4P2.3P2.2P2.1P2.0EARSTXTAL2GNDXTAL1ALEPSEN/RXD/TXD/INT0/INT1/T0/T1/WR/RD40393837363534333231302928272625242322211234567891011121314151617181920A0/D0/A1/D1/A2/D2/A3/D3/A4/D4/A5/D5/A6/D6/A7/D7/A8/A9/A10/A11/A12/A13/A14/A15/P0口分时作为数据线和片外存储器低8位地址线。单片机扩展片外存储器时P2口输出片外存储器地址高8位电源引脚单片机外部引脚时钟引脚VCC（40脚）GND（20脚）控制引脚并行I/O口引脚：XTAL1（19脚）XTAL2（18脚）复位引脚RST（9脚）地址锁存允许引脚ALE（30脚）外部程序存