Theory flashcards

Question 1

What can be found at address 0000 of the AVR data memory?

Answer 1

The first general purpose register from the register block

Question 2

What is the effect of the instruction: sbic PORTC, 5?

Answer 2

skips over the next instruction if the bit 5 of register PORTC is cleared

Question 3

Difference between ld and ldi

Answer 3

ld = load
Loads one byte indirect with or without displacement from the data space to a register.
ldi = load immediate
Loads an 8 bit constant directly to register 16 to 31.

Question 4

What is the purpose if the TCCR0 register of AVR?

Answer 4

The configuration of the Timer can be set using the TCCR0

Question 5

What is a 3-state buffer?

Answer 5

A tri-state buffer is similar to a buffer, but it adds an additional “enable” input that controls whether the primary input is passed to its output or not. If the “enable” inputs signal is true, the tri-state buffer behaves like a normal buffer. If the “enable” input signal is false, the tri-state buffer passes a high impedance (or hi-Z) signal, which effectively disconnects its output from the circuit.

Question 6

What is Arduino function for disabling an external interrupt?

Answer 6

De-activating the interrupt handling process is done by calling the function
detachInterrupt(), with the syntax:
detachInterrupt(interrupt)
interrupt - interrupt number

Question 7

What are the interrupt types of a 16-bit AVR timer?

Answer 7

Events that are generating interrupts:
• Overflow
• Compare match
• External event (capture) – available only for 16 bits timers

Question 8

What is the Arduino function to generate a signal of a given frequency.

Answer 8

tone(pin, frequency, duration) – causes a signal of given ‘frequency’ on the specified
‘pin’, for ‘duration’ milliseconds.

Question 9

Give an example of a serial interface that uses master-slave configuration and one example

Answer 9

USES – SPI

DOES NOT USE – USART

Question 10

What are the signals for the UART communication?

Answer 10

The basic UART signals:
Rx – input, reception
Tx – output, transmission

Question 11

What is the meaning of Serial.begin(9600,SERIAL_9E2)?

Answer 11

Serial.begin(speed, config) – configures speed (speed) + selects other data
formats (config)
+ slide UART of arduino

Question 12

Phase and polarity of the SPI communication?

Answer 12

CPOL – clock polarity – whether the first edge is rising or falling
• CPHA – clock phase
• For CPHA = 0: (for = 1 is reversed)
• Latch data on the first clock edge
• Shift (set up) the data on the second clock edge

Question 13

What is a stepper motor?

Answer 13

•The rotation is achieved step by step, by selective activation of the coils
• The currents in the coils are changed by electronic control, unlike the classical DC
motors which use mechanical control (brushes)

Question 14

BHE signal of 8086 purpose?

Answer 14

BHE – Byte high enable
WE (from the 82C08), BHE and A0 are used to determine if a write is to be performed
and which byte(s) (low or high or both) is to be written.

Question 15

What is 8259 required to place on the bus when it recieves INTA signal?

Answer 15

PIC puts on the bus the interrupt number (type) for the requested interrupt.

Question 16

What are the steps of a DMA fly-by transfer?

Steps

Answer 16

slide “Types of DMA transfer”
1) The DMA controller requests bus access, using the HOLD pin.
2) 8086 finishes the current bus cycle, and enters the HOLD state.
3) 8086 grants bus access by activating the HOLDA pin. The bus access pins of
8086 (address, commands, data) are set to high impedance.
4) The DMA transfer is performed.
5) When the DMA transfer is finished, the DMA controller de-activates HOLD, to
release the control of the bus.

Question 17

Which AVR register can be used with immediate instructions?

Answer 17

R16-R31

Question 18

What is the effect of cbi PORTC,5?

Answer 18

set bit 5 of PORTC to zero

Question 19

What is the difference between ld r1,X+ and ld r1, +X?

Answer 19

ld r0, X+ access location pointed by X, then increment X

ld r0, +X increment X, then access location pointed by X

Question 20

What is the purpose of EICRA?

Answer 20

Configuring the mode of sensing external interrupts – registers EICRA and
EICRB – a total of 16 bits, 2 bits / interrupt

Question 21

What is a Pull Up resistor?

Answer 21

= resistor used to ensure a known state for a signal

Holds the input pin to logic ‘1’ when the button is released

Question 22

Arduino function for disabling the interrupt system?

Answer 22

noInterrupts()

Question 23

What is an output compare register of a timer?

Answer 23

this register is always compared against TCNT0. when equal to TCNT0 the output compare flag is set (OCF0) and an interrupt can be issued.

Question 24

Which are the signals of the 8086 that are involved in the DMA transfer?

Answer 24

HOLD, HLDA

Question 25

What is the size in bytes of the interrupt vector table?

Answer 25

from f000h to ffffh. 1024 bytes

Question 26

What is the purpose of DEN signal of 8086?

Answer 26

Data enable. DEN is active low(0) during each memory and input-output access and for INTA cycles.

Question 27

What is a servo motor?

Answer 27

•Use of a feedback mechanism to maintain a given position, set by a control signal
(analog or digital)
•Contains a DC motor, gears, and a control circuit.

Question 28

What is the principle of distance measurement using sonar?

Answer 28

When triggered, the ultrasonic sensor generates eight acoustic (ultrasonic) wave bursts and initiates a time counter. As soon as the reflected (echo) signal is received, the timer stops. The output of the ultrasonic sensor is a high pulse with the same duration as the time difference between transmitted ultrasonic bursts and the received echo signal.
The microcontroller interprets the time signal into distance using the following functions:

Question 29

What is the difference between single ended input and differential input for the A/D convertor?
16.

Answer 29

for single ended: difference between the voltage at an input and ground
for differential input: converts the difference between the voltage at one input and the voltage at another input that is not necessarily ground.

Question 30

What are the options for A/D reference voltage configuration for Arduino Mega?

Answer 30

Selectable 2.56V or 1.1V internal ADC Reference Voltage

Question 31

What are the signals involved in an SPI communication?

Answer 31

SCLK, MOSI,MISO,SS

Question 32

What is the meaning of Wire.begin(0x21)?

Answer 32

activates the I2C interface. The address parameter indicates the 7-bit address that Arduino will use on the I2C bus as a slave. If no address is given, the device will be set up as master.

Question 33

Arduino function for generating a PWM signal?

Answer 33

Calling the function analogWrite (pin, value) causes a PWM signal to be generated on
the ‘pin’, having a duty cycle specified by ‘value’.

Question 34

What is the duty cycle of a PWM signal?

Answer 34

A duty cycle or power cycle is the fraction of one period in which a signal or system is
active.