In 8051, Pin number 30 is used:

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 1
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  1. To control the signal to enable the external memory
  2. To control the demultiplexing address and data bus
  3. for I/O ports
  4. for the interface of external devices

Answer (Detailed Solution Below)

Option 2 : To control the demultiplexing address and data bus
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Detailed Solution

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8051 microcontroller is a 40-Pin DIP (dual in-line package).

F2 S.B 15.9.20 Pallavi D 3

  • PIN 30 is called ALE (address latch enable). It is used to control the demultiplexing of address and data bus.
  • PIN 31 is called external Access Enable (EAE) Pin and used for external program memory access.
  • PIN 29 is called program store enable (PSEN) Pin and is used to read external program memory.
  • PIN 18 and 19 are used to control clock pulse generated by a quartz crystal oscillator.


Important Points:

PIN Diagram of 8051 Microcontroller.

NOTE: PORT 0 to 3, all bidirectional input / output pins.

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