ARM-specific Functions

10.15uart.c interface functions

The majority of the functions in uart.c involve interfacing between the modem dialer code in dialer.c and the UART hardware.

Each UART within the system has a UART structure associated with it:

Most of the fields within this structure are used for statistics gathering and are not particularly important. The more important fields are:

The interface functions are as follows:

•uart_getc() on page 10-23

•uart_DCD() on page 10-24

•uart_delay() on page 10-24

ARM-specific Functions

•uart_do_irq() on page 10-25

•uart_init() on page 10-26

•uart_irq() on page 10-26

•uart_putc() on page 10-27

•uart_ready() on page 10-27

•uart_reset() on page 10-28

•uart_setup() on page 10-29

•uart_stats() on page 10-30.

10.15.1 uart_getc()

This function reads a character from a UART. It retrieves a character from the receive ring buffer, if available, and returns it to the caller.

Syntax

int uart_getc(int unit)

where:

Return value

Returns one of the following:

character

the character returned from the ring buffer, if available.

ARM-specific Functions

10.15.2 uart_DCD()

This function returns the Data Carrier Detect (DCD) state.

Syntax

int uart_DCD(int unit)

where:

Return value

Returns one of the following:

TRUE if the carrier detect line or signal is down.

FALSE if the carrier detect line or signal is up.

Usage

This function is used by the modem dialer code to monitor the state of the DCD input.

10.15.3 uart_delay()

This function causes a delay for a specified number of clock ticks.

Syntax

static void uart_delay(unsigned long ticks)

where:

ticks is the number of clock ticks to delay for.

Return value

None.

Usage

This function can be used to block execution for a short amount of time. This function loops, calling YIELD(), until the number of ticks specified has elapsed. Ticks occur TPS times per second. TPS is defined in the ipport.h file. See Timers and multitasking on page 2-8 for more information.

ARM-specific Functions

10.15.4 uart_do_irq()

This function handles interrupts for a specific UART.

Syntax

static void uart_do_irq(struct uart *pUart)

where:

pUart is the pointer to the UART structure of the interrupting UART.

Usage

This function is called from the uart_irq() function when it has determined which UART has caused the interrupt. It examines the interrupt status from the UART and processes the interrupt accordingly.

For line status and modem status interrupts, no processing is done other than to clear the source of the interrupt.

If the interrupt was caused because there are characters available in the receive FIFO, these characters are added to the receive ring buffer. If the receive ring buffer is full, the extra characters are read from the UART and discarded.

If the interrupt was caused by a transmit interrupt, up to 16 characters are copied from the transmit ring buffer to the UART transmit FIFO.

If the transmit ring buffer is emptied, transmit interrupts are no longer appropriate, so they are disabled.