A typical device for expanding the 8051 ports is the 8255A Programmable Peripheral Interface. i) Provide a functional description of the 8255A Programmable Peripheral Interface device, describing the sequence of steps necessary to permit writing to the upper nibble of Port C (CU) and reading from the 8255A’s lower nibble of Port C. ii) If both Port A and Port B are used for output and Port C is used as described in
A typical device for expanding the 8051 ports is the 8255A Programmable Peripheral
Interface.
i) Provide a functional description of the 8255A Programmable Peripheral Interface
device, describing the sequence of steps necessary to permit writing to the upper
nibble of Port C (CU) and reading from the 8255A’s lower nibble of Port C.
ii) If both Port A and Port B are used for output and Port C is used as described in
part (i) above, state the value that should be placed in the 8255A control register.
iii) Assuming Port C can only be read in a byte-wise manner into the 8051
accumulator, state how you would remove the influence of the upper nibble when
performing a comparison test. Provide a suitable assembly language statement to
achieve this.
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