The 8085 Microprocessor has Serial Input/Output lines consisting of two pins as follows:
1. Serial Output Data (SOD) 2. Serial Input Data (SID)
They both are specially made for Input/Output which is further controlled by software. The transfer of data is controlled with the help of two instructions, i.e, SIM and RIM.
Now, let’s see both the pins one-by-one:
- Serial Output Data (SOD):
The SIM Instruction should be initiated in order to output data in serial manner. This is done through the SOD Line.Examples:
Instructions:
MVI A, 80H : Set D7 in the accumulator=1
RAR : Set D6 = 1 and bring carry into D7
SIM : Output D7In the above set of instructions, the serial output line is enabled by rotating 1 into bit position D6; the instruction SIM outputs the carry bit through bit position D7.
It can be represented as:
Figure – Interpretation by SIM Instruction - Serial Input Data (SID):
In SID, the RIM Instruction is initiated to input data in a serial manner. This is done through SID line.
It can be represented as:
Figure – Interpretation by RIM Instruction
Advantage:
In a software controlled Input/Output system, the SID and SOD lines eliminate the need of an input and output port respectively.
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