Chapter 3

Question 1

What is SFR TCON

Answer 1

A register used to control timers such as start, stop, reset etc

Question 2

What is SFR TMOD

Answer 2

A register used to configure how timers operate

Question 3

What do timer data registers do?

Answer 3

The timer data registers store the current value of the timer as the timer is incremented this value increases

Question 4

Modern timer operations

Comparator

Answer 4

A value written to register is compared in hardware to timer counter. If value is equal then comparator flag = 1 or interrupt called.

Question 5

Modern timer operations

Capture

Answer 5

The current counter value is captured and written to a register in hardware. Usually triggered from an interrupt.

Question 6

Modern timer operations

Prescaler

Answer 6

Integer divisor to lower frequency of ticks.

Question 7

Loop timeouts

Answer 7

Loop timeouts used to ensure exit from loops

Variable is initialised and then incremented until overflow

Question 8

Hardware timeouts

Answer 8

More precise than loop timeouts. A timer is configured with required timeout delay and timer flag is monitored

Question 9

Interrupts

Answer 9

Based on an event, a signal is sent to pause its current program execution and execute some code associated with the event.

Question 10

External interrupts

Answer 10

External interrupts are those that are generated by signals external to the chip.