The 1747-L553 master device sends data to the GPRS module when the GPRS module sends the signal to the GPRS network, the master device must indicate the destination address of the data, only then the network in the diagram above can select the route for data transmission, processing and transmission of this set of data. The network transmits this data to the destination GPRS module, which then transmits the data to the connected slave device. The difference between the two transmission methods is that the RS485 bus does not use the destination address during transmission, it is a broadcast transmission method.

The GPRS network of the 1747-L553 selects the transmission route based on the destination address of the data at the beginning of the transmission, which is a point-to-point transmission for each transmission. When using a GPRS module to organize a network, the destination address of the data transmission must be given according to the data format of the GPRS module. Therefore, the transmission format of the GPRS module cannot be transparent. In RS485 bus communication, in order to avoid data conflict on the bus, it is necessary to use question-and-answer communication. GPRS network, on the other hand, allows many sites to send data to one site simultaneously. The ordering of data arriving at the destination site is accomplished by the network.

The 1747-L553 module is used in two modes, one is the format transmission mode. The other is transparent transmission mode. Module transmission format can not be transparent and G200-type GPRS module and transparent transmission mode? In fact, the transparent transmission mode of the serial port and the serial port of the device to transmit data although no format, but the destination address of the data is implicitly specified. The destination address of the data is saved in the EEROM, which is read into the ROM after the module is powered up, and the module turns the unformatted data of the serial port into formatted data containing the destination address when sending data.