SynopsisExtended16550< DefaultBaudRate > Struct Template Reference

The Synopsis extended 16550 UART has two additional registers that are not part of a standard 16550, one of which allows for fractional multipliers. More...

#include <platform-uart.hh>

Inheritance diagram for SynopsisExtended16550< DefaultBaudRate >:

Collaboration diagram for SynopsisExtended16550< DefaultBaudRate >:

Public Member Functions
void	init (unsigned baudRate=DefaultBaudRate, unsigned timerFrequency=CPU_TIMER_HZ) volatile
	Initialise the UART.
Public Member Functions inherited from Uart16550< uint32_t >
bool	can_write () volatile
	Returns true if the transmit buffer is empty.
bool	can_read () volatile
	Returns true if the receive buffer is not.
uint8_t	blocking_read () volatile
	Read one byte, blocking until a byte is available.
void	blocking_write (uint8_t byte) volatile
	Write one byte, blocking until the byte is written.
void	init (int divisor=1, T &&otherSetup=no_custom_init) volatile
	Initialise the UART.

Public Attributes
uint32_t	loopback
	Loopback register.
uint32_t	divisorLatchFraction
	Divisor latch fraction.
Public Attributes inherited from Uart16550< uint32_t >
uint32_t	data
	The interface to the read/write FIFOs for this UART.
uint32_t	intrEnable
	Interrupt-enabled control / status.
uint32_t	intrIDandFifo
	Interrupt identification and FIFO enable/disable.
uint32_t	lineControl
	Specifies properties of the line (stop bit, parity, and so on).
uint32_t	modemControl
	Modem control.
const uint32_t	LineStatus
	The line status word.
const uint32_t	ModemStatus
	Modem status.
uint32_t	scratch
	Scratch register.

Static Public Attributes
static constexpr uint32_t	BaudScaleFactorShift = 4
	The divisor is calculated from 16 times the baud rate.
static constexpr uint32_t	BaudFractionBits = 4
	The value in divisorLatchFraction is truncated to this many bits.

Detailed Description

template<unsigned DefaultBaudRate = 115'200>
struct SynopsisExtended16550< DefaultBaudRate >

The Synopsis extended 16550 UART has two additional registers that are not part of a standard 16550, one of which allows for fractional multipliers.

This is always instantiated with 32-bit device registers. The default baud rate is set as a template parameter and can be overridden in init.

Definition at line 15 of file platform-uart.hh.

Member Function Documentation

init()

template<unsigned DefaultBaudRate = 115'200>

void SynopsisExtended16550< DefaultBaudRate >::init ( unsigned baudRate = DefaultBaudRate, unsigned timerFrequency = CPU_TIMER_HZ ) volatile

inline

Initialise the UART.

Definition at line 50 of file platform-uart.hh.

References BaudScaleFactorShift, Uart16550< uint32_t >::blocking_write(), divisorLatchFraction, and Uart16550< RegisterType >::init().

Member Data Documentation

BaudFractionBits

template<unsigned DefaultBaudRate = 115'200>

uint32_t SynopsisExtended16550< DefaultBaudRate >::BaudFractionBits = 4

staticconstexpr

The value in divisorLatchFraction is truncated to this many bits.

Definition at line 45 of file platform-uart.hh.

BaudScaleFactorShift

template<unsigned DefaultBaudRate = 115'200>

uint32_t SynopsisExtended16550< DefaultBaudRate >::BaudScaleFactorShift = 4

staticconstexpr

The divisor is calculated from 16 times the baud rate.

The baud rate is in the range of KHz to hundreds of KHz, whereas the clock frequency is typically tens to hundreds of MHz. The divisor must fit in a 16-bit integer (written across two 8-bit device registers) and so is scaled to ensure that it fits (by a power of two, which makes it trivial to reverse the multiplication in the hardware).

Definition at line 40 of file platform-uart.hh.

Referenced by init().

divisorLatchFraction

template<unsigned DefaultBaudRate = 115'200>

uint32_t SynopsisExtended16550< DefaultBaudRate >::divisorLatchFraction

Divisor latch fraction.

When the divisor latch is set (for writing the divisor), this is used for the fraction. RS-232 requires a 3% tolerance for the baud rate and an integer divisor over the clock frequency of the host may not get within this range. This register is used to provide a 4-bit correction that allows baud rates to stay within the required range.

Definition at line 30 of file platform-uart.hh.

Referenced by init().

loopback

template<unsigned DefaultBaudRate = 115'200>

uint32_t SynopsisExtended16550< DefaultBaudRate >::loopback

Loopback register.

Unused.

Definition at line 20 of file platform-uart.hh.

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The documentation for this struct was generated from the following file:

• sdk/include/platform/synopsis/platform-uart.hh