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用RAM作为通讯场所能够使这种主从系统迅速实现多组数据的井行通讯与传统的并行通讯相比,具有软件设计简单,通讯准确,通讯机之间无需协议应答信号,因而可以大大节约系统的通讯时间,尤其适合于快速的实时控制系统.以两片616 RAM和八片74LS245收发器为例,实现63路八位数据的快速并行通讯.硬件接口电路如图1所示.八片74LS245收发器作为开关使用,分别用于RAM的地址线和数据线的选通控制,其中芯片1,2,3,4,用于地址线,芯片5,6,7,8用于数据线.锁存器74LS74等芯片作为保存切换两片RAM的控制信息使用,构成了电路的存储,读取数据的控制口(在本例电路中该控制口地址为03FH).当从机单片机需要存储数据时,可先向控制口写入1或0,该信息通过锁存器,三态门,反相器分别控
Compared with the traditional parallel communication, this kind of master-slave system can quickly realize the well-to-do communication of multiple sets of data with RAM as a communication place, and has the advantages of simple software design, accurate communication, and no need for protocol reply signals between the communication devices, thereby greatly saving System communication time, especially for fast real-time control system to two 616 RAM and eight 74LS245 transceiver, for example, to achieve 63 fast eight-bit parallel data communication hardware interface circuit shown in Figure 1. Eight 74LS245 transceiver used as a switch, respectively, for the RAM address line and data strobe control, which chip 1,2,3,4, for address lines, chip 5,6,7,8 for data lines. Latch 74LS74 and other chips as a switch to save the control information switching two RAM used to form the circuit to store and read data control port (in this case the circuit control port address 03FH.) When the need to store data from the microcontroller , You can first write to the control port 1 or 0, the information through the latch, tri-state gate, the inverter control