Lab 7 Tasks

Requested Functions

• int uart_config(uint16_t base, uint32_t baud, uint8_t line_control)
• int uart_enable_fifo(uint16_t base)
• int uart_enable_rx_interrupt(uint16_t base)
• int uart_set_loopback(uint16_t base, int enabled)
• int uart_send_byte(uint16_t base, uint8_t byte)
• int uart_read_byte(uint16_t base, uint8_t *byte)
• int uart_subscribe(uint8_t irq, lcom_irq_t *out)
• int uart_unsubscribe(lcom_irq_t *irq)

Guided Gaps

• Validate base port and baud rate.
• Compute divisor from the UART base clock.
• Preserve line-control bits around divisor-latch access.
• Add timeouts for send/read waits.
• Keep loopback setup independent from normal configuration.

IMPORTANT

Always restore line-control state after touching the divisor latch. Otherwise later reads and writes may go to the wrong logical register.

Common Mistakes

• Forgetting divisor-latch access before writing the divisor.
• Forgetting to clear divisor-latch access after configuration.
• Sending without checking transmitter-ready.
• Treating "no byte" as "received byte 0".

Next: checks and references.