Question

Consider the following statement(s)

1. In 8085, 16-bit address bus, which can address up to 64KB  

2. HOLD signal indicates that another master is requesting the use of the address and data buses.

3. MVI K, 20F is an example of Immediate addressing mode

Which of the above statement(s) is/are correct?

1. Only 1 
2. Only 1 and 2
3. All
4. Only 2 and 3
5.

Answer 1

Correct Answer - Option 3 : All

8085 microprocessor data and address bus:

• 8085 has 8-bit data and 16 address bits.
• Hence it has 216 memory locations
• Memory size is 2¹⁶ = 64 Kb
• 8085 has 8 data lines which are multiplexed with address lines (AD0- AD7)

HOLD:

• When the HOLD pin is activated by an external signal, the microprocessor relinquishes control buses and allows the external peripheral to use them.
• It completes the execution of the current instruction and then stops execution.
• For example, the HOLD signal is used Direct memory access (DMA) data transfer.
• In this DMA, the external Input / Output devices are directly communicating with the memory without interfering with the processor every time.
• This signal indicates that another master is requesting the use of the address and data buses.

Immediate addressing mode::

• In this mode, the 8/16-bit data is specified in the instruction itself as one of its operands.
• For example MVI K, 20F: means 20F is copied into register K.
• The operand is the number given in the instruction itself.
• In immediate addressing mode, the source operand is always data.
• If the data is 8-bit, then the instruction will be of 2 bytes, if the data is 16-bit then the instruction will be of 3 bytes.