Lab 2 Tasks

Requested Functions

• int timer_set_frequency(uint8_t timer, uint32_t freq)
• int timer_get_conf(uint8_t timer, uint8_t *status)
• int timer_subscribe(lcom_irq_t *irq)
• int timer_unsubscribe(lcom_irq_t *irq)
• void timer_ih(void)
• uint32_t timer_ticks(void)

Guided Gaps

• Reject invalid timer numbers and impossible frequencies.
• Build the control word from fields.
• Split a 16-bit divisor into low and high bytes.
• Track ticks without relying on wall-clock time.
• Make subscribe and unsubscribe symmetric.

IMPORTANT

Interrupt handlers should not contain large application logic. Record the device event, then let the main loop decide what to do.

Common Mistakes

• Dividing in the wrong direction.
• Accepting a divisor of zero.
• Writing only one byte of the divisor.
• Counting ticks in the main loop instead of in the handler.

Next: checks and references.