FMA Unit 4.5 Operating Modes of Serial Port

Operating Modes of Serial Port

Mode 0:

•     It is a uniprocessor mode.
•      In this mode of serial port, synchronous communication is used. It is 8-bit shift register mode.
•         There are TWO 8-bit shift register which are PISO and SIPO shift register.
•           Two signals i.e. data signals and clock signals are used in this mode.
•          Data is transmitted and received by RxD pin and clocks are provided with the help of TxD pin.
•         PxD pin is used for transmitting the data through SIPO and for receiving the data from PISO.
•       With this arrangement, data can be transmitted to parallel device and data can be received from parallel device. 
•         In the mode there is Fixed Baud Rate (f_osc / 12)

Mode 1: (Standard 8-bit UART mode)

•         It is a uniprocessor, synchronous serial communication mode.
•           It is used to transfer data between 8051 and peripheral devices.
•         In this mode data is transmitted or received by asynchronous manner. i,e 1 start bit, 8 bit data, 1 stop (Framing of 10-bit) will be transmitted or received.
•         In this mode, Baud rate is variable and which is decided by timer 1 overflow rate. Timer 1 in mode 2 is used to control the baud rate.
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Mode 2: (9-bit UART mode with fixed baud rate)

•          It is a multiprocessor, synchronous serial communication mode.
•          It is used to transfer data between 8051 and peripheral devices.
•          Generally used to transfer the data between two micro-controller.
•         In this mode data is transmitted or received by asynchronous manner. i,e 1 start bit, 8 bit data, 1  9^th programmable bit, 1 stop (Framing of 11-bit) will be transmitted or received.
•         In this mode, Baud rate is fixed.
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Mode 3: (9-bit UART mode with variable baud rate)

•         It is a multiprocessor, synchronous serial communication mode.
•         It is used to transfer data between 8051 and peripheral devices.
•         Generally used to transfer the data between two micro-controller.
•         In this mode data is transmitted or received by asynchronous manner. i,e 1 start bit, 8 bit data, 1  9^th programmable bit, 1 stop (Framing of 11-bit) will be transmitted or received.
•         In this mode, Baud rate is variable and which is decided by timer 1 overflow rate. Timer 1 in mode 2 is used to control the baud rate.
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