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> AT91SAM7S деление, Вопрос о реализации опереции деления
ZiB
сообщение Mar 19 2009, 05:31
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Всем, привет!

Осваиваю AT91SAM7S256. Eclipse + GCC + SAM-ICE.
Запустил демо проект с сайта at91.com (getting-started-project-1.4-at91sam7s-ek)

В функции конфигурации DBGU модуля, установка (точнее расчет) скорости обмена занимает почти 3 секунды.
AT91C_BASE_DBGU->DBGU_BRGR = mck / (baudrate * 16); // mck = 48 000 000, baudrate = 9600
так как апаратного деления у ARM-а нет, то деление происходит программным способом.

Вопрос:
Насколько оптимально производит деление компилаятор gcc?
в сравнении с IAR-ом?

Планирую в проекте использовать цело численное деление.

CODE
void DBGU_Configure(unsigned int mode,
unsigned int baudrate,
unsigned int mck)
{
// Reset & disable receiver and transmitter, disable interrupts
AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RSTRX | AT91C_US_RSTTX;
AT91C_BASE_DBGU->DBGU_IDR = 0xFFFFFFFF;

// Configure baud rate
AT91C_BASE_DBGU->DBGU_BRGR = mck / (baudrate * 16);

// Configure mode register
AT91C_BASE_DBGU->DBGU_MR = mode;

// Disable DMA channel
AT91C_BASE_DBGU->DBGU_PTCR = AT91C_PDC_RXTDIS | AT91C_PDC_TXTDIS;

// Enable receiver and transmitter
AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RXEN | AT91C_US_TXEN;
}
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ZiB
сообщение Mar 19 2009, 10:33
Сообщение #2


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хух, все встало на свои места после того как убрал -mlong-calls из Makefile...
сейчас разбираюсь что за штука.
Хотя во всех примерах Makefile содержит данную опцию.
CODE
# ----------------------------------------------------------------------------
# ATMEL Microcontroller Software Support
# ----------------------------------------------------------------------------
# Copyright © 2008, Atmel Corporation
#
# 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 disclaimer below.
#
# Atmel's name may not be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
# DISCLAIMED. IN NO EVENT SHALL ATMEL 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.
# ----------------------------------------------------------------------------

# Makefile for compiling the Getting Started project

#-------------------------------------------------------------------------------
# User-modifiable options
#-------------------------------------------------------------------------------

# Chip & board used for compilation
# (can be overriden by adding CHIP=chip and BOARD=board to the command-line)
CHIP = at91sam7s256
BOARD = at91sam7s-ek

# Optimization level, put in comment for debugging
#OPTIMIZATION = -Os

# AT91 library directory
AT91LIB = ../at91lib

# Output file basename
OUTPUT = getting-started-project-$(BOARD)-$(CHIP)

# Compile for all memories available on the board (this sets $(MEMORIES))
include $(AT91LIB)/boards/$(BOARD)/board.mak

# Output directories
BIN = bin
OBJ = obj

#-------------------------------------------------------------------------------
# Tools
#-------------------------------------------------------------------------------

# Tool suffix when cross-compiling
CROSS = arm-elf-

# Compilation tools
CC = $(CROSS)gcc
SIZE = $(CROSS)size
STRIP = $(CROSS)strip
OBJCOPY = $(CROSS)objcopy

# Flags
INCLUDES = -I$(AT91LIB)/boards/$(BOARD) -I$(AT91LIB)/peripherals
INCLUDES += -I$(AT91LIB)/components -I$(AT91LIB)

CFLAGS = -mlong-calls -ffunction-sections -Wall
CFLAGS += -g $(OPTIMIZATION) $(INCLUDES) -D$(CHIP) #-DNOTRACE
ASFLAGS = -g $(OPTIMIZATION) $(INCLUDES) -D$(CHIP) -D__ASSEMBLY__
LDFLAGS = -g $(OPTIMIZATION) -nostartfiles -Wl,--gc-sections

#-------------------------------------------------------------------------------
# Files
#-------------------------------------------------------------------------------

# Directories where source files can be found
UTILITY = $(AT91LIB)/utility
PERIPH = $(AT91LIB)/peripherals
BOARDS = $(AT91LIB)/boards

VPATH += $(UTILITY)
VPATH += $(PERIPH)/dbgu $(PERIPH)/aic $(PERIPH)/pio $(PERIPH)/pit $(PERIPH)/tc
VPATH += $(BOARDS)/$(BOARD) $(BOARDS)/$(BOARD)/$(CHIP)

# Objects built from C source files
C_OBJECTS = main.o
C_OBJECTS += led.o stdio.o
C_OBJECTS += dbgu.o pio.o aic.o pio_it.o pit.o tc.o
C_OBJECTS += board_memories.o board_lowlevel.o

# Objects built from Assembly source files
ASM_OBJECTS = board_cstartup.o

# Append OBJ and BIN directories to output filename
OUTPUT := $(BIN)/$(OUTPUT)

#-------------------------------------------------------------------------------
# Rules
#-------------------------------------------------------------------------------

all: $(BIN) $(OBJ) $(MEMORIES)

$(BIN) $(OBJ):
mkdir $@

define RULES
C_OBJECTS_$(1) = $(addprefix $(OBJ)/$(1)_, $(C_OBJECTS))
ASM_OBJECTS_$(1) = $(addprefix $(OBJ)/$(1)_, $(ASM_OBJECTS))

$(1): $$(ASM_OBJECTS_$(1)) $$(C_OBJECTS_$(1))
$(CC) $(LDFLAGS) -T"$(AT91LIB)/boards/$(BOARD)/$(CHIP)/$$@.lds" -o $(OUTPUT)-$$@.elf $$^
$(OBJCOPY) -O binary $(OUTPUT)-$$@.elf $(OUTPUT)-$$@.bin
$(SIZE) $$^ $(OUTPUT)-$$@.elf

$$(C_OBJECTS_$(1)): $(OBJ)/$(1)_%.o: %.c Makefile
$(CC) $(CFLAGS) -D$(1) -c -o $$@ $$<

$$(ASM_OBJECTS_$(1)): $(OBJ)/$(1)_%.o: %.S Makefile
$(CC) $(ASFLAGS) -D$(1) -c -o $$@ $$<
endef

$(foreach MEMORY, $(MEMORIES), $(eval $(call RULES,$(MEMORY))))

clean:
-rm -f $(OBJ)/*.o $(BIN)/*.bin $(BIN)/*.elf

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