MOVX instruction is used to access external memory locations.ħ. This means that memory space used to access 8255 (i.e.
Why MOVX instruction is being used to access the ports of the 8255?Ī) because 8255 is connecting a microcontroller in memory mapped I/O configurationī) because 8255 is used to access the external communicationĬ) because 8255 is used to access the data transferĭ) because 8255 is used to access the interfacing of LCD, motor etcĬlarification: As 8255 is connecting a microcontroller in memory mapped I/O configuration. Hence the value of the control register remains the same as it is even when the RESET button is set to zero.Ħ.
set to high), all ports are initialized as input mode. What is the value of the control register when RESET button is set to zero?Ĭlarification: RESET is active-high signal input into the 8255 used to clear the control register. A0 and A1 pins are used for select ports and the control register.ĥ. Which pins are used to select the ports and the control register?Ĭlarification: CS pin is an active low input pin for 8255 and it is used for selecting a chip. Find the control word for PA = out, PB = in, PCL = out, PCH = out (Mode0)?Ĭlarification: The value that is being loaded in the control word is 10000010b for PB as an input port and all others as the output ports being operated in mode0.
Which pins of a microcontroller are directly connected with 8255?Ĭlarification: RD, WR, D0-D7 all are directly connected to the 8051 for telling the chip about the control signals and also for transferring the data.ģ. The 8255 chip is used to expand the I/O ports of microcontrollers.Ģ. 8051 Micro-controller Multiple Choice Questions on “Interfacing with 8255”.Ĭlarification: The 8255 is Input/Output (I/O) chip.
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