Chapter 3: Further Microcontrollers

Question 1

What is the structure of the main program code

Answer 1

Label Command Operand ; comments

Question 2

Give three examples of input devices

Answer 2

Microswitch
Temperature sensor
Microphone

Question 3

Give three examples of output components

Answer 3

LED
Motor
Speakes

Question 4

Describe the architecture of a microcontroller

Answer 4

Input port connected to the CPU from the left
Output port connected to the CPU from the right
Memory connected to the CPU from above
Clock connected to the CPU from the bottom

Question 5

Name the two types of microcontroller memory

Answer 5

Program memory and Data memory

Question 6

What do vectors do?

Answer 6

Tell the processor what to do in specific events

Question 7

What is the reset vector address?

Answer 7

0000h
It contains a goto command followed by a label at the start of the program

Question 8

What is the interrupt vector address?

Answer 8

0004h
It contains a goto command and a label at the start of the program

Question 9

What is a subroutine?

Answer 9

They carry out operations that can be used many times.
They are short sections of program in an area of memory outside the main program.

Question 10

How would you jump to a subroutine?

Answer 10

Using the call command

Question 11

How would you jump back to the main program from a subroutine

Answer 11

Using the return command

Question 12

How would you configure PortA

Answer 12

Using the TrisA command

Question 13

How would you configure portB

Answer 13

Using the TrisB command

Question 14

How would you configure a bit to be an input in portA?

Answer 14

Put a logic 1 in TrisA

Question 15

How would you configure a bit to be an output in portA?

Answer 15

Put a logic 0 in TrisA

Question 16

Describe the interrupt service routine step by step

Answer 16

1. Interrupt is detected
2. Completes the instruction it is currently executing
3. Stores the contents of the program center on the stack
4. Loads the interrupt vector address 0004h
5. Executes the instruction found here

Question 17

What is the stack?

Answer 17

An area of program memory used to store return addresses

Question 18

What are the three bits we use from the INTCON register

Answer 18

Bit 1,4 and 7

Question 19

What is bit 7 from the INTCON register

Answer 19

The global interrupt bit (GIE)

Question 20

What does a logic 1 at bit7 GIE cause?

Answer 20

Enables all interrupt sources

Question 21

What does a logic 0 at bit 7 GIE cause?

Answer 21

Disables all the interrupt sources

Question 22

What is bit 4 on the INTCON register?

Answer 22

External interrupt enable bit (INT0IE)

Question 23

What does a logic 1 at bit 4 INT0IE cause?

Answer 23

Enables the interrupt

Question 24

What does a logic 0 at bit 4 INT0IE cause?

Answer 24

Disables the interrupt

Question 24

What is bit 1 on the INTCON register?

Answer 24

The external interrupt flag (INT0IF)

Question 25

What does a logic 1 at bit 1 INT01F cause?

Answer 25

Interrupt occurred

Question 26

What does a logic 0 at bit 1 INT01F cause?

Answer 26

No interrupt occured

Question 27

What must be set to respond to an interrupt?

Answer 27

Bit 7 GIE

Question 28

ISR must clear an interrupt otherwise what will happen?

Answer 28

The interrupt will run completly

Question 29

Is the GIE cleared automatically if yes, then how?

Answer 29

With a retfie command.
Note: Return command will not do this