The Universal Asynchronous Receiver Transmitter (UART) has the same features as that of the standard 8051 microcontrollers. It means that it can operate in 1 out of 4 different modes, which is controlled by bits SM0 and SM1 of the SCON register.
Microcontroller B: SADDR = 1100 0000 SADEN = 1111 1101 Address = 1100 00X0 Microcontroller C: SADDR = 1100 0000 SADEN = 1111 1110 Address = 1100 000XAlthough both microcontrollers B and C are assigned the same address (1100 0000), the mask in register SADEN is used to differentiate between them. It enables the master to communicate with both of them separately or at the same time: If transmit address is 1100 0010, the data will be sent to slave device B. If transmit address is 1100 0001 the data will be sent to slave device C. If transmit address is 1100 0000 the data will be sent to both slave devices.