Struct uart8250::MmioUart8250

pub struct MmioUart8250<'a> { /* private fields */ }

MMIO version of an 8250 UART.

Note This is only tested on the NS16550 compatible UART used in QEMU 5.0 virt machine of RISC-V.

Implementations

impl<'a> MmioUart8250<'a>

pub unsafe fn new(base_address: usize) -> Self

Creates a new UART.

Safety

The given base address must point to the 8 MMIO control registers of an appropriate UART device, which must be mapped into the address space of the process as device memory and not have any other aliases.

pub fn init(&self, clock: usize, baud_rate: usize)

Initialises the UART with common settings and interrupts enabled.

More customised initialisation can be done using other methods below.

pub unsafe fn set_base_address(&mut self, base_address: usize)

Sets a new base address for the UART.

Safety

The given base address must point to the 8 MMIO control registers of an appropriate UART device, which must be mapped into the address space of the process as device memory and not have any other aliases.

pub fn read_byte(&self) -> Option<u8>

Reads a byte from the UART.

Returns None when data is not ready (RBR[0] != 1)

pub fn write_byte(&self, byte: u8) -> Result<(), TransmitError>

Writes a byte to the UART.

pub fn set_divisor(&self, clock: usize, baud_rate: usize)

Sets DLAB to true, sets divisor latch according to clock and baud_rate, then sets DLAB to false.

Divisor Latch Bytes

Offset: +0 and +1 . The Divisor Latch Bytes are what control the baud rate of the modem. As you might guess from the name of this register, it is used as a divisor to determine what baud rate that the chip is going to be transmitting at.

Used clock 1.8432 MHz as example, first divide 16 and get 115200. Then use the formula to get divisor latch value:

DivisorLatchValue = 115200 / BaudRate

This gives the following table:

Baud Rate	Divisor (in decimal)	Divisor Latch High Byte	Divisor Latch Low Byte
50	2304	$09	$00
110	1047	$04	$17
220	524	$02	$0C
300	384	$01	$80
600	192	$00	$C0
1200	96	$00	$60
2400	48	$00	$30
4800	24	$00	$18
9600	12	$00	$0C
19200	6	$00	$06
38400	3	$00	$03
57600	2	$00	$02
115200	1	$00	$01

pub fn write_ier(&self, value: u8)

Write IER (offset + 1)

Write Interrupt Enable Register to turn on/off interrupts

pub fn is_low_power_mode_enabled(&self) -> bool

get whether low power mode (16750) is enabled (IER[5])

pub fn enable_low_power_mode(&self)

enable low power mode (16750) (IER[5])

pub fn disable_low_power_mode(&self)

disable low power mode (16750) (IER[5])

pub fn is_sleep_mode_enabled(&self) -> bool

get whether sleep mode (16750) is enabled (IER[4])

pub fn enable_sleep_mode(&self)

enable sleep mode (16750) (IER[4])

pub fn disable_sleep_mode(&self)

disable sleep mode (16750) (IER[4])

pub fn is_modem_status_interrupt_enabled(&self) -> bool

get whether modem status interrupt is enabled (IER[3])

pub fn enable_modem_status_interrupt(&self)

enable modem status interrupt (IER[3])

pub fn disable_modem_status_interrupt(&self)

disable modem status interrupt (IER[3])

pub fn is_receiver_line_status_interrupt_enabled(&self) -> bool

get whether receiver line status interrupt is enabled (IER[2])

pub fn enable_receiver_line_status_interrupt(&self)

enable receiver line status interrupt (IER[2])

pub fn disable_receiver_line_status_interrupt(&self)

disable receiver line status interrupt (IER[2])

pub fn is_transmitter_holding_register_empty_interrupt_enabled(&self) -> bool

get whether transmitter holding register empty interrupt is enabled (IER[1])

pub fn enable_transmitter_holding_register_empty_interrupt(&self)

enable transmitter holding register empty interrupt (IER[1])

pub fn disable_transmitter_holding_register_empty_interrupt(&self)

disable transmitter holding register empty interrupt (IER[1])

pub fn is_received_data_available_interrupt_enabled(&self) -> bool

get whether received data available is enabled (IER[0])

pub fn enable_received_data_available_interrupt(&self)

enable received data available (IER[0])

pub fn disable_received_data_available_interrupt(&self)

disable received data available (IER[0])

pub fn read_fifo_status(&self) -> ChipFifoInfo

Read IIR[7:6] to get FIFO status

pub fn is_64byte_fifo_enabled(&self) -> bool

get whether 64 Byte fifo (16750 only) is enabled (IIR[5])

pub fn read_interrupt_type(&self) -> Option<InterruptType>

Read IIR[3:1] to get interrupt type

pub fn get_parity(&self) -> Parity

get parity of used data protocol

pub fn set_parity(&self, parity: Parity)

set parity

pub fn get_stop_bit(&self) -> u8

get stop bit of used data protocol

Simply return a u8 to indicate 1 or 1.5/2 bits

pub fn set_stop_bit(&self, stop_bit: u8)

set stop bit, only 1 and 2 can be used as stop_bit

pub fn get_word_length(&self) -> u8

get word length of used data protocol

pub fn set_word_length(&self, length: u8)

set word length, only 5..=8 can be used as length

pub fn is_received_fifo_error(&self) -> bool

get whether there is an error in received FIFO

pub fn is_data_holding_registers_empty(&self) -> bool

Gets whether data holding registers are empty, i.e. the UART has finished transmitting all the data it has been given.

pub fn is_transmitter_holding_register_empty(&self) -> bool

Gets whether transmitter holding register is empty, i.e. the UART is ready to be given more data to transmit.

pub fn is_break_interrupt(&self) -> bool

pub fn is_framing_error(&self) -> bool

pub fn is_parity_error(&self) -> bool

pub fn is_overrun_error(&self) -> bool

pub fn is_data_ready(&self) -> bool

pub fn is_carrier_detect(&self) -> bool

pub fn is_ring_indicator(&self) -> bool

pub fn is_data_set_ready(&self) -> bool

pub fn is_clear_to_send(&self) -> bool

pub fn is_delta_data_carrier_detect(&self) -> bool

pub fn is_trailing_edge_ring_indicator(&self) -> bool

pub fn is_delta_data_set_ready(&self) -> bool

pub fn is_delta_clear_to_send(&self) -> bool

pub fn read_sr(&self) -> u8

pub fn write_sr(&self, value: u8)