Embedded

Question 1

What is the role of the ACC register?

Answer 1

Main ALU operand/result register.

Question 2

What is the B register used for?

Answer 2

Multiplication and division instructions.

Question 3

Purpose of DPTR?

Answer 3

16-bit pointer for MOVX external memory access.

Question 4

What is the PSW register?

Answer 4

Program Status Word: CY, AC, OV, P, RS1/RS0.

Question 5

What are RS1 and RS0?

Answer 5

Bits selecting register bank 0–3.

Question 6

Default stack pointer value?

Answer 6

07h.

Question 7

Which port requires external pull-ups?

Answer 7

Port 0.

Question 8

Purpose of Port 3?

Answer 8

Alternate functions: INT0, INT1, T0, T1, RXD, TXD, WR, RD.

Question 9

Address range for internal RAM?

Answer 9

00h–7Fh.

Question 10

Address range for SFRs?

Answer 10

80h–FFh.

Question 11

Bit-addressable RAM range?

Answer 11

20h–2Fh.

Question 12

Bit-addressable SFRs example?

Answer 12

TCON, PSW, ACC, B, Ports.

Question 14

What does CY flag indicate?

Answer 14

Carry flag.

Question 15

What does AC represent?

Answer 15

Auxiliary carry for BCD operations.

Question 16

What does OV indicate?

Answer 16

Signed overflow.

Question 17

What does P indicate?

Answer 17

Parity: 1=odd, 0=even.

Question 18

When does parity flip?

Answer 18

Whenever number of 1s in ACC changes.

Question 19

When does overflow occur?

Answer 19

If signed addition exceeds range -128 to +127.

Question 21

Timer tick duration at 11.0592MHz?

Answer 21

1.085 microseconds.

Question 22

Timer Mode 1 bit-width?

Answer 22

16-bit.

Question 23

Timer Mode 2 bit-width?

Answer 23

8-bit auto-reload.

Question 24

Meaning of C/T=0?

Answer 24

Counts internal clock (timer).

Question 25

Meaning of C/T=1?

Answer 25

Counts external pulses (counter).

Question 26

Formula for delay counts?

Answer 26

counts = delay / 1.085us.

Question 27

Formula for load value?

Answer 27

Load = 65536 - counts.

Question 28

Start Timer 0?

Answer 28

TR0 = 1.

Question 29

Stop Timer 0?

Answer 29

TR0 = 0.

Question 30

Timer 0 input pin?

Answer 30

T0 on P3.4.

Question 31

Timer 1 input pin?

Answer 31

T1 on P3.5.

Question 32

Gate bit=1 meaning?

Answer 32

Timer runs only when INT pin is high.

Question 34

Global interrupt enable bit?

Answer 34

EA (IE.7).

Question 35

Timer 0 interrupt enable bit?

Answer 35

ET0 (IE.1).

Question 36

External interrupt 0 enable bit?

Answer 36

EX0 (IE.0).

Question 37

Vector for INT0?

Answer 37

0003h.

Question 38

Vector for Timer 0?

Answer 38

000Bh.

Question 39

Vector for INT1?

Answer 39

0013h.

Question 40

Vector for Timer 1?

Answer 40

001Bh.

Question 41

Vector for Serial interrupt?

Answer 41

0023h.

Question 42

Instruction ending ISR?

Answer 42

RETI.

Question 43

Difference between RET and RETI?

Answer 43

RETI re-enables interrupt logic.

Question 44

What generates INT0?

Answer 44

Edge or level depending on TCON.

Question 45

TCON bit for INT0 edge sensitivity?

Answer 45

IT0.

Question 46

What does IE control?

Answer 46

Interrupt enables.

Question 47

What does IP control?

Answer 47

Interrupt priority.

Question 49

UART Mode 1 description?

Answer 49

8-bit UART with variable baud.

Question 50

Serial data register?

Answer 50

SBUF.

Question 51

Serial configuration register?

Answer 51

SCON.

Question 52

What does REN do?

Answer 52

Enables receiver.

Question 53

What does TI indicate?

Answer 53

Transmit complete.

Question 54

What does RI indicate?

Answer 54

Receive complete.

Question 55

Baud rate formula?

Answer 55

Baud = (2^SMOD / 32)*(XTAL / (12*(256-TH1))).

Question 56

TH1 for 9600 baud at 11.0592MHz?

Answer 56

FDh.

Question 57

TH1 for 4800 baud at 11.0592MHz?

Answer 57

FAh.

Question 58

What is SMOD?

Answer 58

Baud rate doubler (PCON.7).

Question 60

ADC digital value formula?

Answer 60

D = Vin / (Vref / 2^n).

Question 61

Resolution definition?

Answer 61

Smallest measurable change in voltage.

Question 62

What is quantisation?

Answer 62

Approximating analog to nearest digital step.

Question 63

10-bit ADC levels?

Answer 63

1024

Question 64

Step size for 5V, 10-bit ADC?

Answer 64

4.88mV.

Question 66

What is a transducer?

Answer 66

Converts physical quantity to electrical signal.

Question 67

Direct vs indirect measurement?

Answer 67

Direct measures actual quantity

Question 68

Gauge factor equation?

Answer 68

GF = (ΔR/R) / ε.

Question 69

Strain equation?

Answer 69

ε = (ΔR/R)/GF.

Question 70

Stress equation?

Answer 70

σ = E * ε.

Question 71

Wheatstone output (single gauge)?

Answer 71

Vo ≈ (Vi/4)*(ΔR/R).

Question 72

Why RTD accurate?

Answer 72

Linear, stable, precise.

Question 73

Thermistor characteristic?

Answer 73

Non-linear, high sensitivity.

Question 74

Thermocouple characteristic?

Answer 74

Wide temp range, low cost.

Question 76

SPI wires?

Answer 76

MISO, MOSI, SCLK, SS.

Question 77

I2C wires?

Answer 77

SDA, SCL.

Question 78

UART wires?

Answer 78

TXD, RXD.

Question 79

SPI duplex mode?

Answer 79

Full duplex.

Question 80

I2C duplex mode?

Answer 80

Half duplex.

Question 81

I2C addressing?

Answer 81

7-bit or 10-bit.

Question 82

What defines SPI clock mode?

Answer 82

CPOL and CPHA.

Question 83

CPOL meaning?

Answer 83

Clock polarity (idle high/low).

Question 84

CPHA meaning?

Answer 84

Clock phase (sample 1st/2nd edge).

Question 85

Which bus allows multi-master?

Answer 85

I2C.

Question 86

Fastest bus?

Answer 86

SPI.

Question 88

Components of an FSM?

Answer 88

States, events, transitions.

Question 89

FSM coding pattern?

Answer 89

Nested switch-case.

Question 90

Why use FSM?

Answer 90

Clarity, structure, reliable behaviour.

Question 91

Example of FSM?

Answer 91

Vending machine.

Question 93

Toggle bit in C?

Answer 93

P1 ^= 0x01

Question 94

Start Timer1?

Answer 94

TR1 = 1

Question 95

Clear Timer 0 flag?

Answer 95

TF0 = 0

Question 96

Send char over UART?

Answer 96

SBUF = c

Question 97

Read a pin?

Answer 97

if(P1 & 0x04){...}

Question 98

Write pin high?

Answer 98

P2 |= 0x20

Question 99

Write pin low?

Answer 99

P2 &= ~0x20

Question 100

Delay loop example?

Answer 100

for(i=0