Subversion Repositories wb4pb

################################################################################

## This sourcecode is released under BSD license.

## Please see http://www.opensource.org/licenses/bsd-license.php for details!

################################################################################

##

## Copyright (c) 2010, Stefan Fischer <Ste.Fis@OpenCores.org>

## All rights reserved.

##

## Redistribution and use in source and binary forms, with or without 

## modification, are permitted provided that the following conditions are met:

##

##  * Redistributions of source code must retain the above copyright notice, 

##    this list of conditions and the following disclaimer.

##  * Redistributions in binary form must reproduce the above copyright notice,

##    this list of conditions and the following disclaimer in the documentation

##    and/or other materials provided with the distribution. 

##  * Neither the name of the author nor the names of his contributors may be 

##    used to endorse or promote products derived from this software without 

##    specific prior written permission.

##

## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 

## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 

## ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 

## LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 

## CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 

## SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 

## INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 

## CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 

## ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 

## POSSIBILITY OF SUCH DAMAGE.

##

################################################################################

## filename: baud_rate_calculator.tcl

## description: tcl-script generating assembler constants for standard baud

##              rates

## todo4user: 1. modify output file path, SYSTEM_CLOCK and BAUD_RATES as needed

##            2. run script with TCL interpreter of your choice, i. e. from

##               ModelSim (R) GUI: Menu->Tools->TCL->Execute Macro...

##            3. copy and paste file content from generated

##               baud_rate_constants.txt to assembler source code

## version: 0.0.0

## changelog: - 0.0.0, initial release

##            - ...

################################################################################

# output file path

cd "e:/home_users/ste.fis/projects/wb4pb/trunk/asm"

# reference clock, normally several MHz

set SYSTEM_CLOCK 50.0E6

# some standard baud rates

set BAUD_RATES {

  300

  600

  1200

  2400

  4800

  9600

  19200

  38400

  57600

  115200

  230400

  460800

  921600

}

# open file handle

set f [open "baud_rate_constants.txt" w]

# baud rate configuration:

# baud_limit = round( system clock frequency / (16 * baud rate) ) - 1

# i. e. 9600 baud at 50 MHz system clock =>

# baud_limit = round( 50.0E6 / (16 * 9600) ) - 1 = 325 = 0x0145

# WARNING, baud rate error should not exceed 1.0 % for reliable operation!

# calculating baud min. and max. values

set baud_max [expr floor($SYSTEM_CLOCK / 16)]

set baud_min [expr ceil($SYSTEM_CLOCK / (16 * 65536))]

puts $f "; baud rate settings for $SYSTEM_CLOCK Hz system reference clock"

puts $f "; max. $baud_max baud"

puts $f "; min. $baud_min baud (16 bit baud timer)"

foreach baud_rate $BAUD_RATES {

  # checking, if current baud rate works with system hardware parameters

  if {[expr $baud_min <= $baud_rate] && [expr $baud_rate <= $baud_max]} {

    # calculating hardware baud timer limit

    set baud_limit [expr round($SYSTEM_CLOCK / (16 * $baud_rate)) - 1]

    # calculating actual hardware baud rate

    set actual_baud_rate [expr $SYSTEM_CLOCK / (16 * ($baud_limit + 1))]

    # calculating baud rate error, value is commented out automatically, if 

    # frequency error is greater than the recommended 1 %

    if {

      [set baud_error [expr abs(($baud_rate / $actual_baud_rate) - 1)]] > 0.01

    } {

      set comment ";"

    } else {

      set comment ""

    }

    # generating a 16 bit, 4 character hexadecimal string of hardware baud timer

    # limit

    set baud_limit_hex [format %04X $baud_limit]

    # creating strings with constant definitions in kcpsm3 assembler syntax,

    # splitting into high and low byte

    puts $f "${comment}CONSTANT UART_BAUD_LO_${baud_rate}_VALUE , [string range\

             $baud_limit_hex 2 3] ; actual baud rate [format %.2f \

             $actual_baud_rate]"

    puts $f "${comment}CONSTANT UART_BAUD_HI_${baud_rate}_VALUE , [string range\

             $baud_limit_hex 0 1] ; => baud rate error [format %.3f [expr 100 *\

             $baud_error]] %"

  }

}

# closing file

close $f