Languages [Hughes Placement]: Sample Questions 6 - 7 of 9

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Question 6

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How many address are required for 4 kilo bytes of memory?

Explanation

8085 is a 8 bit processor, where data lines are 8 bits and address lines are 16 bits.

To address 64 kilo bytes of memory we need to use 16 address lines.

Same way, to address 32 kilo bytes of memory 15 address lines are used. Remaining 1 address line is used to enable the chip.

To address 16 kilo bytes of memory, 14 address lines are used.

To address 8 kilo bytes of memory, 13 address lines are used.

To address 4 kilo bytes of memory, 12 address lines are used.

Question 7

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Using which pin it՚s possible to address 16 bit addresses even though there are only 8 address bits in 8085?

Explanation

  • ALE stands for Address Latch Enable.
  • It is used in 8085 microprocessor to demultiplex the address bus and data bus of the microprocessor. 8 bit data bus and 16 bit address bus is present in 8085, where lower order address bus are multiplexed with data bus. Low order AD0 and AD7 are multiplexed.
  • When ALE = 1, it indicates the address bus, i.e.. during first clock cycle of the instruction it gives the address
  • When ALE = 0, it indicates the data bus, i.e.. during second and third cycle of instruction it does the operation on data.
  • So, ALE pin is used to demultiplex the lower order address and data bus.

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