Digital Test 1

part A. To allow input signal flow from the pin to the data bus, the gate labelled A must be enabled with a logic ____.

part B. Assume 8 switches are connected to PORTD. Write the code to enable this gate.

Logic 1 (high), TRISD = 0xFF;

unsigned char switchState;

switchState = PORTB & 0x0C;

Assume that 4 active low switches are connected to the lower nibble of PORTB and the port is configured properly. If all four switches are not pressed, what value will switchState contain if the code "switchState = PORTB & 0x0C;"  executes?

0x0C

How many pins are available on PORTB for students to use when the Snap debugger is attached?

6 pins

Timer0 may be configured as a 16-bit timer/counter?

True

Write a for loop to initialize each element of the array with -99.9

for(int i; i < size; i++) { arrayOne[i] = -99.9; }

In MPLAB the Special Functions Registers(SFRs) are set-up to configure Timer0. What is the proper name of the SFR you would need to set-up to  select 8-bit or 16-bit timer?

T0CON

unsigned char var1;

var1= 0x08;

var1 = var1 << 1;

After the code above executes, var1 will contain ______.

0x10

Timer0 preload value is used to achieved specific value between the minimum and maximum values at given configurations

True

Write the declaration to create storage for 120 temperature readings. Each temperature measure is in the range of 10 to 120 degrees Celsius. 

float temperatures [120];

At least one stop bit must be present between data transfer.

True

unsigned char switchState;

Assume that 4 active low switches (SW3-SW0) are connected to the lower nibble of PORTB (RB3:RB0) and the port is configured properly. If SW0 is pressed, what value will switchState contain if the following code executes?

switchState = PORTB & 0x0F; 

0x0E

What is the result of 0b0110 | 0b1100 ?

0b1110

Wiring RS232 port so the the signals are input directly into a PIC will likely result in damage.

True

In RS232 communications, when the transmit line is not active (not transmitting), the pin rests at logic "1".

True

unsigned char var1;

var1= 0x88;

var1 = var1 >> 1;

After the code above executes, var1 will contain ______.

0x44

RS232 is a mechanical and electrical standard. Logic 0 is considered if a signal is in the range of _____ volts to _____ volts

+3 V to +15 V

unsigned char var1;

var1= 0x1F;

var1 = var1 >> 5;

After the code above executes, var1 will contain ______.

0x00

When using MCC to enable serial communications for the 18f45k22, one of two EUSARTs must be selected.

True

What is the result of 0b0110 & 0b1100 ?

0b0100

unsigned char switchState;

Assume that 4 active low switches (SW3-SW0) are connected to the lower nibble of PORTB (RB3:RB0) and the port is configured properly. If SW3 is pressed, what value will switchState contain if the following code executes?

switchState = (PORTB & 0x0F)>>3;

0x00

The following SFRs are needed to be configured for EUSART1

RCSTA1, TRISC, TXSTA1, and BAUDCON1

What standard C function must be called before "truely" random numbers can be generated?

srand()

The oscillator frequency selected for PIC operation does not affects the BAUD rates that are available.

False

RS232 is an example of a NRZ (Non-Return-to-Zero) waveform.

True

Write a code segment (not a full program) to fill an array of size 50 with random numbers in the range 10 to 120

for (int i = 0; i < 50; i++) { arrayOne[i] = (rand() % 111) + 10;}

unsigned char switchState;

Assume that 4 active low switches (SW3-SW0) are connected to the lower nibble of PORTB (RB3:RB0) and the port is configured properly. If the SW2 and SW1 are pressed, what value will switchState contain if the following code executes?

switchState = (~PORTB & 0x0F)>>1; 

0×03

Timer0 overflow flag is automatically reset by MAPLAB X MCC software

False

How many EUSART ports are available in PIC18F45K22?

2 ports

In MPLAB the Special Functions Registers(SFRs) are set-up to configure Timer0. What is the proper name of the SFR you would need to set-up to  selecte prescaler value for  Timer 0.

T0CON

Timer 0 may be configured to count external events that occur on an external pin.

True

What register controls the data direction of a ports pins? i.e: what register must be configured to make a pin act as an input or output. (Proper spelling as it is used in C code)

TRIS = 0 for output, TRIS = 1 for input

RS232 is a mechanical and electrical standard. Logic 1 is considered if  a signal is in the range of _____ volts to _____ volts

−3 V to −15 V

List the states the gate marked with A can output?

Logic 0, Logic 1, and High-Impedance (High-Z)

Write c-code to reset Timer0 overflow flag

INTCONbits.TMR0IF = 0;

unsigned char var1;

var1= 0x80;

var1 = var1 >> 1;

After the code above executes, var1 will contain ______.

0x40

unsigned char var1;

var1= 0x80;

var1 = var1 >> 4;

After the code above executes, var1 will contain ______.

0x08

In serial communications the least significant bit is the first data bit to be sent.

True

The Snap debugger supplies power to your breadboard.

False

There are 3 Timer0 Prescaler Selection bits. This allows the programmer to select 1 out of ____ prescaler values.

8 values

Write the code to initialize the lower nibble of port B to be inputs and the upper nibble to be outputs.

TRISB = 0x0F;

RC7 is dedicated TX pin for RS232 port in PIC18F45K22.

True

In MPLAB the Special Functions Registers(SFRs) are set-up to configure Timer0. What is the proper name of the SFR you would find Timer0 overflow (rollover) flag?

INTCON

The current value held by Timer 0 may be read.

True

Calculate the rate in HZ at which timer0 changes if the PIC18f45k22 has its internal oscillator set to 4MHz and a prescaler of 2 is selected

500kHz

In general, interrupt sources have three bits to control their operation. They are:

• Flag bit : to indicate that an interrupt event occurred

• Enable bit: that allows program execution to branch to the interrupt vector address when the flag bit is set

• Priority bit: to select if the interrupt subroutine at address _______ or address ________  is dispatched

0x0008, 0x0018

Explain what effect would setting the #defined symbol TMR0_INTERRUPT_TICKER_FACTOR to 1 have? ie: #define TMR0_INTERRUPT_TICKER_FACTOR 1

Setting it to 1 means the program counts every Timer0 interrupt instead of skipping some.

EUSART1 can be assigned to a high or low priority

True

Timer 0 can be assigned to a high or low priority

True

To allow a counter variable to be incremented or decremented in the callback function, such as flashLED_ISR( ), but the counter is use to control LEDs (such as LED Toggle) within the main loop, what type of variable is required? (ie: global, local, static, etc...)

Global variable

The Timer0 interrupt is generated when the Timer0 count register overflows from FFFFFFh to 000000h in 16-bit mode

False

The oscillator frequency is divided by 8 before entering into the Timer0 block.

True

In lecture example codes, the callback function flashLED_ISR( ) is called every time Timer0 overflows.

True

You can call interrupt subroutine functions from within main safely.

False

In what MCC generated file does #define symbol TMR0_INTERRUPT_TICKER_FACTOR exist?

mcc.h

In the 18f45k22 , high priority interrupts can be enabled while the low priority interrupts are disabled BUT Low priority interrupts can ONLY be enabled if the high priority interrupts are enabled.

False

What is the maximum number of levels of priority interrupts within the 18f45k22?

2 levels

When the prescaler is assigned to Timer0, 3 bits control the prescaler value thus enabling the selection of prescale values of 1:2 through 1:512 in integer power-of-2 increments.

False

In main, what function is required to be enabled in order for Timer0 interrupts to work?

INTERRUPT_GlobalInterruptEnable();