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1. 8051 series of micro controllers are made by which of the following companies?
a) Atmel
b) Philips
c) None of the mentioned
d) Both of the mentioned

Answer: d [Reason:] Atmel series AT89C2051 and Philips family P89C51RD2 are the two most common micro controllers of 8051 family.

2. AT89C2051 has RAM of:
a) 128 bytes
b) 256 bytes
c) 64 bytes
d) 512 bytes

Answer: b [Reason:] It has 128 bytes of RAM in it.

3. 8051 series has how many 16 bit registers?
a) 2
b) 3
c) 1
d) 0

Answer: a [Reason:] It has two 16 bit registers DPTR and PC.

4. When 8051 wakes up then 0x00 is loaded to which register?
a) DPTR
b) SP
c) PC
d) PSW

Answer: c [Reason:] When a program wakes up, then 0x00 is loaded to the program counter register because at this place the first op code is burnt.

5. When the micro controller executes some arithmetic operations, then the flag bits of which register are affected?
a) PSW
b) SP
c) DPTR
d) PC

Answer: a [Reason:] It stands for program status word. It consists of carry, auxiliary carry, overflow, parity, register bank select bits etc which are affected during such operations.

6. How is the status of the carry, auxiliary carry and parity flag affected if write instruction
MOV A,#9C
a) CY=0,AC=0,P=0
b) CY=1,AC=1,P=0
c) CY=0,AC=1,P=0
d) CY=1,AC=1,P=1

Answer: b [Reason:] On adding 9C and 64, a carry is generated from D3 and from the D7 bit so CY and AC are set to 1. In the result, the number of 1’s present are even so parity flag is set to zero.

7. How are the bits of the register PSW affected if we select Bank2 of 8051?
a) PSW.5=0 and PSW.4=1
b) PSW.2=0 and PSW.3=1
c) PSW.3=1 and PSW.4=1
d) PSW.3=0 and PSW.4=1

Answer: d [Reason:] Bits of PSW register are CY, AC, F0, RS1, RS0, OV, -, P so for selecting bank2 RS1=1 and RS0=0 which are fourth and third bit of the register respectively.

8. If we push data onto the stack then the stack pointer
a) increases with every push
b) decreases with every push
c) none of the mentioned
d) both of the mentioned

Answer: a [Reason:] If we push elements onto the stack then the stack pointer increases with every push of element.

9. On power up, the 8051 uses which RAM locations for register R0- R7
a) 00-2F
b) 00-07
c) 00-7F
d) 00-0F

Answer: b [Reason:] On power up register bank 0 is selected which has memory address from 00H-07H.

10. How many bytes of bit addressable memory is present in 8051 based micro controllers?
a) 8 bytes
b) 32 bytes
c) 16 bytes
d) 128 bytes