Microprocessor – Serial IO (Serial Output Data,Serial Input Data)

Serial Input / Output data using 8085


8085 Microprocessor has two Serial Input/Output pins that are used to read/write one bit data to and from peripheral devices.


SID (Serial Input Data) line

  • There is an One bit Input line inside the 8085 CPU (Pin number 5)
  • 1 bit data can be externally read and stored using this SID line
  • The data that is read is stored in the A7th bit of the Accumulator
  • RIM instruction is used to read the SID line





SOD (Serial Output Data) Line

  • There is a One bit Output port inside the 8085 CPU (Pin number 4
  • 1 bit data can be externally written in this port.
  • To write data into this port, SIM instruction is used.
  • The data that is to be written in this port must be stored in the A7th bit of the
  • Bit A6 of the Accumulator is known as SOE (Serial output Enable). This bit
    Must be set to 1 to enable Serial data output.


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