Multi-computer communication refers to a network structure composed of more than two single-chip computers, which realizes data exchange and control through serial communication. The network topology of multi-computer communication includes star, ring and master-slave structure, among which the master-slave structure is widely used.
When the master wants to send a data block to the slave, it first sends an address byte, which is called an address frame, and its 9th bit is "1". At this time, when the 9th bit (RB8) received by the serial port of each slave device is 1, the interrupt flag RI is set to "1" so that each slave device can check the received address. If it is the address of the local machine, clear SM2, while other slaves keep SM2= 1.
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Because the system integrates multiple processors, each processor is equivalent to a host of the system, and all processors need to share resources for communication. At present, the mainstream multiprocessor communication modes are: shared memory communication mechanism, mailbox hardware communication mechanism, DMA data processing communication mechanism, serial port master-slave mode communication mechanism.
Similarly, the slave processor cannot update data to the corresponding storage area during communication. Therefore, it is necessary to consider the transmission and processing time. The advantage of adopting serial master-slave communication mode is that it is less dependent on software programs, and the disadvantage is that it is somewhat dependent on internal circuit structure, and the transmission mode is single and takes a long time. If complex communication protocols are designed, the pressure of software programming will be great.
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