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I/O PORTS AND SPECIAL FUNCTION REGISTERS
3.8.1 | Comparing 8255 PPI with MCS-51 Ports
If the reader has already studied 8085 or 8086 microprocessor, then 8255 I/O port would not be unfamiliar.
However, there are some major diff erences between 8255 PPI and MCS-51 ports apart from the diff erences in
their numbers and nomenclature.
In 8255, there are three ports named A, B and C whereas in MCS-51 there are four ports designated as P0,
P1, P2 and P3. In 8255, ports were byte programmable (all 8 bits would be either input or output) whereas in
MCS-51 they are bit programmable. 8255 ports may work in any one of the three modes, namely Mode 0, Mode ...