Engineering Questions with Answers - Multiple Choice Questions

# MCQs on Register Set of 8051

1 - Question

Which of the following is an 8-bit register?
a) PSW(Program Status Word)
b) TCON(Timer Control Register)
c) Accumulator
d) All of the mentioned

Explanation: The registers, PSW, TCON and Accumulator are 8-bit registers.

2 - Question

Which of the following register can be addressed as a byte?
a) P1
b) SCON
c) TMOD
d) TCON

Explanation: The registers, TMOD, SP, TH0, TH1, TL0, TL1 are to be addressed as bytes.

3 - Question

Which of the following is bit-addressable register?
a) SBUF
b) PCON
c) TMOD
d) SCON

Explanation: The registers, accumulator, PSW, B, P0, P1, P2, P3, IP, IE, TCON and SCON are all bit-addressable registers.

4 - Question

The higher and lower bytes of a 16-bit register DPTR are represented respectively as
a) LDPTR and HDPTR
b) DPTRL and DPTRH
c) DPH and DPL
d) HDP and LDP

Explanation: The registers, DPH and DPL are the higher and lower bytes of a 16-bit register DPTR.

5 - Question

The register that is used for accessing external data memory is
a) DPH
b) DPL
c) DPTR
d) NONE

Explanation: The Data Pointer(DPTR) is used for accessing external data memory which means that it includes both DPH and DPL.

6 - Question

Among the four groups of register banks, the number of groups that can be accessed at a time is
a) 1
b) 2
c) 3
d) all the four

Explanation: At a time, only one of the four register banks can be accessed.

7 - Question

The number of 8-bit registers that a register bank contain is
a) 2
b) 4
c) 6
d) 8

Explanation: The 32, 8-bit registers are divided into four groups of 8 registers each, called register banks.

8 - Question

If RS1=1, RS0=0, then the register bank selected is
a) register bank 0
b) register bank 1
c) register bank 2
d) register bank 3

Explanation: If RS1=1, RS0=0, then the register bank selected is register bank 2.

9 - Question

If RS1=1, RS0=1, then the register bank selected is
a) register bank 0
b) register bank 1
c) register bank 2
d) register bank 3

Explanation: If RS1=1, RS0=1, then the register bank selected is register bank 3. If RS1=0, RS0=0, then selected bank is register bank 0.

10 - Question

The PCON register consists of
a) power mode bit
b) power idle bit
c) power ideal bit
d) power down bit and idle bit

Explanation: The power control register, PCON consists of power down bit and idle bit which activate the power down mode and idle mode in 80C51BH.

11 - Question

The on-chip oscillator is stopped in
a) power mode
b) power down mode
c) idle mode
d) ideal mode

Explanation: In power down mode, the on-chip oscillator is stopped.

12 - Question

In idle mode, the device that is disabled is
a) serial port
b) timer block
c) clock to CPU
d) all of the mentioned

Explanation: In idle mode, the oscillator continues to run and the interrupt, serial port and timer blocks are active but the clock to the CPU is disabled.

13 - Question

The only way to terminate the power down mode is to
a) CLEAR
b) RESET
c) HOLD
d) HLT

Explanation: The only way to terminate the power down mode is hardware reset. The reset redefines all the SFRs but the RAM contents are left unchanged.

14 - Question

The idle mode can be terminated by
a) PRESET
b) CLEAR
c) Interrupt
d) Interrupt or reset