Subversion Repositories openrisc_2011-10-31

/* uart.c. UART support functions
 
   Copyright (C) 2004, Jacob Bower
   Copyright (C) 2010, Embecosm Limited <info@embecosm.com>
 
   Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>
 
   This file is part of Newlib.
 
   The original work by Jacob Bower is provided as-is without any kind of
   warranty. Use it at your own risk!
 
   All subsequent work is bound by version 3 of the GPL as follows.
 
   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 3 of the License, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   more details.
 
   You should have received a copy of the GNU General Public License along
   with this program.  If not, see <http:#www.gnu.org/licenses/>.             */
/* -------------------------------------------------------------------------- */
/* This program is commented throughout in a fashion suitable for processing
   with Doxygen.                                                              */
/* -------------------------------------------------------------------------- */
 
#include "or1k-support.h"
#include "uart.h"
 
/*! Macro to access a UART register */
#define UREG8(reg) REG8 (_board_uart_base + reg)
 
/*! Macro to check if transmit and transmit holding registers are both empty. */
#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
 
/*! Macro to wait until a char has been transmitted */
#define WAIT_FOR_XMITR				\
  do						\
    {						\
      lsr = UREG8 (UART_LSR);			\
    }						\
  while ((lsr & BOTH_EMPTY) != BOTH_EMPTY)
 
/*! Macro to wait until a char can be transmitted */
#define WAIT_FOR_THRE				\
  do						\
    {						\
      lsr = UREG8 (UART_LSR);			\
    }						\
  while ((lsr & UART_LSR_THRE) != UART_LSR_THRE)
 
/* Macro to see if a character has been received */
#define CHECK_FOR_CHAR (UREG8 (UART_LSR) & UART_LSR_DR)
 
/* Macro to wait until a character is received */
#define WAIT_FOR_CHAR \
         do { \
                lsr = UREG8 (UART_LSR); \
         } while ((lsr & UART_LSR_DR) != UART_LSR_DR)
 
 
/* -------------------------------------------------------------------------- */
/*!Initialize the UART                                                        */
/* -------------------------------------------------------------------------- */
void
__uart_init ()
{
	int divisor;
 
	/* Reset receiver and transmiter */
	UREG8 (UART_FCR) = UART_FCR_ENABLE_FIFO |
	                   UART_FCR_CLEAR_RCVR  |
	                   UART_FCR_CLEAR_XMIT  |
	                   UART_FCR_TRIGGER_14;
 
	/* Disable all interrupts */
	UREG8 (UART_IER) = 0x00;
 
	/* Set 8 bit char, 1 stop bit, no parity */
	UREG8 (UART_LCR) = UART_LCR_WLEN8 & ~(UART_LCR_STOP | UART_LCR_PARITY);
 
	/* Set baud rate */
	divisor = (_board_clk_freq / _board_uart_baud + 8) / 16;
 
	UREG8 (UART_LCR) |= UART_LCR_DLAB;
	UREG8 (UART_DLL)  = divisor & 0x000000ff;
	UREG8 (UART_DLM)  = (divisor >> 8) & 0x000000ff;
	UREG8 (UART_LCR) &= ~(UART_LCR_DLAB);
 
}	/* __uart_init () */
 
 
/* -------------------------------------------------------------------------- */
/*!Put a character out on the UART
 
   @param[in] c  The character to output				      */
/* -------------------------------------------------------------------------- */
void __uart_putc (char  c)
{
  unsigned char lsr;
 
  /* Wait until we are free to transmit */
  WAIT_FOR_THRE;
 
  /* Put the character to be transmitted and wait until it has gone. */
  UREG8 (UART_TX) = c;
  WAIT_FOR_XMITR;
 
}	/* __uart_putc () */
 
 
/* -------------------------------------------------------------------------- */
/*!Get a character from the UART
 
   @reurn  The character read.                                                */
/* -------------------------------------------------------------------------- */
char
__uart_getc ()
{
  unsigned char lsr;
  char c;
 
  /* Wait until a char is available, then get it. */
  WAIT_FOR_CHAR;
 
  return  UREG8 (UART_RX);
 
}	/* __uart_getc () */