Microprocessor Multiple Choice Questions on “Register Set of 8051”.
1. 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
Answer: d
Clarification: The registers, PSW, TCON and Accumulator are 8-bit registers.
2. Which of the following register can be addressed as a byte?
a) P1
b) SCON
c) TMOD
d) TCON
Answer: c
Clarification: The registers, TMOD, SP, TH0, TH1, TL0, TL1 are to be addressed as bytes.
3. Which of the following is bit-addressable register?
a) SBUF
b) PCON
c) TMOD
d) SCON
Answer: d
Clarification: The registers, accumulator, PSW, B, P0, P1, P2, P3, IP, IE, TCON and SCON are all bit-addressable registers.
4. 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
Answer: c
Clarification: The registers, DPH and DPL are the higher and lower bytes of a 16-bit register DPTR.
5. The register that is used for accessing external data memory is
a) DPH
b) DPL
c) DPTR
d) NONE
Answer: c
Clarification: The Data Pointer(DPTR) is used for accessing external data memory which means that it includes both DPH and DPL.
6. 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
Answer: a
Clarification: At a time, only one of the four register banks can be accessed.
7. The number of 8-bit registers that a register bank contain is
a) 2
b) 4
c) 6
d) 8
Answer: d
Clarification: The 32, 8-bit registers are divided into four groups of 8 registers each, called register banks.
8. 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
Answer: c
Clarification: If RS1=1, RS0=0, then the register bank selected is register bank 2.
9. 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
Answer: d
Clarification: 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. The PCON register consists of
a) power mode bit
b) power idle bit
c) power ideal bit
d) power down bit and idle bit
Answer: d
Clarification: 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. The on-chip oscillator is stopped in
a) power mode
b) power down mode
c) idle mode
d) ideal mode
Answer: b
Clarification: In power down mode, the on-chip oscillator is stopped.
12. In idle mode, the device that is disabled is
a) serial port
b) timer block
c) clock to CPU
d) all of the mentioned
Answer: c
Clarification: 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. The only way to terminate the power down mode is to
a) CLEAR
b) RESET
c) HOLD
d) HLT
Answer: b
Clarification: 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. The idle mode can be terminated by
a) PRESET
b) CLEAR
c) Interrupt
d) Interrupt or reset
Answer: d
Clarification: The idle mode can be terminated with a hardware interrupt or hardware reset signal.