数字硬件测试题(英文版)

是大学三年级的数字硬件英文版本的题目

ECTE333: Digital Hardware 2

Spring Session 2008 ─ Class Test ─ Solution

Time: 60 minutes | Total marks: 20 | Worth: 5% of annual subject

1. Serial Port [5 marks]

a) Determine the value of relevant ATmega16 registers for serial transmission at a baud rate of

1200bps, eight data bits, one start bit, one stop bit, no parity bit, system clock 1MHz.

b) Explain the difference between the steps to send and receive a character through the serial port of

the ATmega16. a) There are four groups of relevant registers.

* UBRRH and UBRRL

UBRR = 1000000/(16 × 1200) ─ 1 = 51d = 0033H.

Therefore, UBRRH = 00H and UBRRL = 33H.

* UCSRA

0000000U2X = 0: normal speed mode

MPCM =0: disable multi-processor communication mode

* UCSRB

000

11RXEN = 1: enable receiver pin

TXEN = 1: enable transmitter pin

UCSZ2 = 0: together with UCSZ1:0 to select data size of 8 bits

UDRIE = 0: disable interrupt

*UCSRC

1000

0UCSZ1:UCSZ0 = 11: together with UCSZ2 to select data size of 8 bits

UPM1:UPM0 = 00: no parity

USBS = 0: 1 stop bit

UMSEL = 0: select asynchronous mode

URSEL = 1: to write to UCSRC register instead of UBRRH

是大学三年级的数字硬件英文版本的题目

b)

Sending

Check until UDRE flag is set to 1.

Write the character to register UDR for transmission.

void USART_send(unsigned char data){

// Wait until UDRE flag = 1

while ((UCSRA & (1<<UDRE)) == 0x00){;}

// Write char to UDR for transmission

UDR = data;

}

Receiving

Check until RXC flag is set to 1.

Read the received character from register UDR.

unsigned char USART_receive(void){

// wait until RXC flag = 1

while ((UCSRA & (1<<RXC)) == 0x00){;}

// Read the received char from UDR

return (UDR);

}

是大学三年级的数字硬件英文版本的题目

2. Timer 1 Input Capture Interrupt [5 marks] State the values of relevant registers, the required connections, and the key steps in the C interrupt-driven program.

Method

The period of a square wave is the time difference between two consecutive rising edges.

Connect the square wave to input capture pin of Timer 1 (ICP1/PD6).

Configure input capture module to trigger on a rising edge.

When input capture interrupt s triggered, read ICR1 register and reset Timer 1.

Required registers

Select timer operations: normal, no prescaler, internal clock 1MHz, noise canceller enabled,

input capture for rising edges.

TCCR1A = 0b00000000;

TCCR1B = 0b11000001;

Enable input capture interrupt:

TIMSK = 0b00100000;

Key steps in C interrupt-driven program: The shaded parts are key steps

#include <avr/io.h>

#include <avr/interrupt.h>

#include <inttypes.h>

int main(void) {

} return 0;

是大学三年级的数字硬件英文版本的题目

3. Pulse Width Modulator [5 marks]

A S3003 servo motor must be driven to an angular position using a PWM signal with a frequency of 50Hz and a duty cycle of 10%. Explain the steps and the relevant registers to produce the required

Period = 1/50Hz = 20000μs and high time = 20000μs £ 10% = 2000μs

Method

o Use Fast PWM mode WGM3:0 = 1110

o The TOP limit TOP is specified by register ICR1,

o Compare match is triggered by the value in register OCR1A.

o Set OC1A when compare match

o Clear OC1A when timer = 0.

Values of registers

1100Register TCCR1A

01Register TCCR1B

o ICR1 = 20000: eriod of output signal.

o OCR1A = 2000: pulse width of output signal.

o WGM3:0 = 1110: fast PWM mode where TOP = ICR1.

o CS12:0 = 001: internal clock, no prescaler.

o COM1A1:0 = 10: set OC1A when timer = 0, clear OC1A when compare match.

Therefore,

DDRD=0b00100000; // set port D for output (D.5 is OC1A)

TCCR1A = 0b10000010;

TCCR1B = 0b00011001;

ICR1 = 20000; // period of output signal

OCR1A = 2000; // pulse width of output signal

是大学三年级的数字硬件英文版本的题目

4. Analogue-to-Digital Converter [5 marks] Write a C program that uses the polling approach to perform analogue-to-digital conversion with the ATmega16.

The input signal is to be connected to pin ADC0.

The AVCC reference voltage and an ADC prescaler factor of 2 are used.

The digital result in two registers ADCH and ADCL is left aligned.

The top 8-bit of the digital result is to be displayed in PORTB.

State the values of relevant registers, and the main steps in your C program. : Step 1: Configure the ADC using registers ADMUX, ADCSRA, and SFIOR.

o What is the ADC source? [ADC0]

o What reference voltage to use? [AVCC]

o Align left or right the result in ADCH, ADCL? [left]

o Enable or disable ADC auto-trigger? [disable]

o Enable or disable ADC interrupt? [disable]

o What is the ADC prescaler? [2]

Step 2: Start ADC operation

o Write 1 to flag ADSC of register ADCCSRA

Step 3: Extract ADC result

o Wait until flag ADSC becomes 0.

o Read result from registers ADCL and then ADCH. 0 1 1 0 0 0 0 0

ADCMUX

ADCCSRA

#include<avr/io.h>

int main (void){

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