Subversion Repositories openrisc

/*

 * Copyright (c) 1998 Ralf Corsepius (corsepiu@faw.uni-ulm.de)

 *

 * See the file COPYING for copyright notice.

 */

#include <math.h>

#include <stdio.h>

#include <stdlib.h>

#include "sci.h"

/*

   n .. baudrate generator source 0,1,2,3

   N .. BRR setting (0..255)

   Phi .. processor baud rate

   B .. bitrate

 */

typedef struct sci_tab {

  unsigned int  B ;

  unsigned int  n ;

  int           N ;

  double        err ;

  } sci_tab_t ;

static unsigned int bitrate [] = {

  50,

  75,

  110,

  134,

  150,

  200,

  300,

  600,

  1200,

  1800,

  2400,

  4800,

  9600,

  19200,

  38400,

  57600,

  115200,

  230400,

  460800

};

static sci_tab_t test_array[4] ;

static void Compute(

  unsigned int n,

  unsigned int B,

  double   Phi,

  struct sci_tab *entry )

{

  int    a = ( 32 << ( 2 * n ) ) * B ;

  entry->n = n ;

  entry->B = B ;

  entry->N = rint( ( Phi / a ) - 1.0 ) ;

  if ( ( entry->N > 0 ) && ( entry->N < 256 ) )

    entry->err =

      ( ( Phi / ( (entry->N + 1) * a ) - 1.0 ) * 100.0 );

  else

  {

    entry->err = 100.0 ;

    entry->n = 255 ;

    entry->N = 0 ;

  }

}

static sci_tab_t *SelectN(

  unsigned int  B,

  double        Phi )

{

  unsigned int i ;

  struct sci_tab* best = NULL ;

  for ( i = 0 ; i < 4 ; i++ )

  {

    double err ;

    Compute( i, B, Phi, &test_array[i] );

    err = fabs( test_array[i].err );

    if ( best )

    {

      if ( err < fabs( best->err ) )

        best = &test_array[i] ;

    }

    else

      best = &test_array[i] ;

  }

  return best ;

}

int shgen_gensci(

  FILE          *file,

  double        Phi ) /* Processor frequency [Hz] */

{

  unsigned int i ;

  fprintf( file,

    "/*\n * Bitrate table for the serial devices (sci) of the SH at %.3f MHz\n"

    " */\n\n", Phi / 1000000.0 );

  fprintf( file,

    "/*\n"

    " * n     .. SMR bits 0,1 : baud rate generator clock source\n"

    " * N     .. BRR bits 0..7: setting for baud rate generator\n"

    " * error .. percentual error to nominal bitrate\n"

    " *   Hitachi's HW manual recommends bitrates with an error less than 1%%\n"

    " *   We experienced values less than 2%% to be stable\n"

    " */\n\n" );

  fprintf( file, "#include <termios.h>\n\n" );

  fprintf( file,

    "static struct sci_bitrate_t {\n"

    "  unsigned char n ;\n"

    "  unsigned char N ;\n"

    "} _sci_bitrates[] = {\n"

    "/*  n    N      error */\n" );

  for ( i = 0 ; i < sizeof(bitrate)/sizeof(int) ; i++ )

  {

    struct sci_tab* best = SelectN( bitrate[i], Phi );

    if ( i > 0 )

      fprintf( file, ",\n" );

    fprintf( file, "  { %1d, %3d } /* %+7.2f%% ; B%d ",

      best->n,

      best->N,

      best->err,

      best->B );

    if ( best->n > 3 )

      fprintf( file, "(unusable) " );

    fprintf( file, "*/" );

  }

  fprintf( file, "\n};\n\n" );

  fprintf( file,

    "int _sci_get_brparms( \n"

    "  tcflag_t      cflag,\n"

    "  unsigned char *smr,\n"

    "  unsigned char *brr )\n"

    "{\n"

    "  unsigned int offset ;\n\n"

    "  offset = ( cflag & ( CBAUD & ~CBAUDEX ) )\n"

    "    + ( ( cflag & CBAUDEX ) ? B38400 : 0 );\n"

    "  if ( offset == 0 ) return -1 ;\n"

    "  offset-- ;\n\n"

    "  if ( _sci_bitrates[offset].n > 3 )  return -1;\n\n"

    "  *smr &= ~0x03;\n"

    "  *smr |= _sci_bitrates[offset].n;\n"

    "  *brr =  _sci_bitrates[offset].N;\n\n"

    "  return 0;\n"

    "}\n" );

  return 0 ;

}