The P0922YU FPS400-24 master control modem dial-up connection details are described in the next section, and the PLC-side modem setup is described in detail here.The PLC-side modem must be initialised to automatically answer incoming calls after the PLC is powered up. The AT command combination for PLC to initialise the modem is called “MODEM driver”. The modem is controlled by Yonghong PLC through Port1, and this software interface is called modem-specific interface.

P0922YU FPS400-24 with 55H as the high octet can set Port1 as the modem-specific interface, in which the PLC will enable the “MODEM driver”, at this time, although the CPU is still using the “standard communication driver” to manage Port1, the CPU will still use the “standard communication driver” to manage Port1. At this time, although the CPU still uses the “standard communication driver” of Yonghong to manage the communication of Port1, it must be connected through the modem, and before the communication, the master control of Port1 is handed over to the “MODEM driver” for management.

P0922YU FPS400-24 can not make any access to PLC. MODEM driver” is to set the modem to receive mode, and wait for the remote modem to dial in, once both the sender and receiver modem online successfully, the PLC immediately out of the receive mode, and enter the online state, Port1 control to Yonghong “standard communication driver” management. Port1 control is managed by Yonghong’s “Standard Communication Driver”.