102 lines
4.6 KiB
C
102 lines
4.6 KiB
C
/****************************************************************************
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* arch/sim/src/up_romgetc.c
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*
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* Copyright (C) 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/arch.h>
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#ifdef CONFIG_ARCH_ROMGETC
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: up_romgetc
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*
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* Description:
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* In Harvard architectures, data accesses and instruction accesses occur
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* on different busses, perhaps concurrently. All data accesses are
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* performed on the data bus unless special machine instructions are
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* used to read data from the instruction address space. Also, in the
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* typical MCU, the available SRAM data memory is much smaller that the
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* non-volatile FLASH instruction memory. So if the application requires
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* many constant strings, the only practical solution may be to store
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* those constant strings in FLASH memory where they can only be accessed
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* using architecture-specific machine instructions.
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*
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* A similar case is where strings are retained in "external" memory such
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* as EEPROM or serial FLASH. This case is similar only in that again
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* special operations are required to obtain the string data; it cannot
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* be accessed directly from a string pointer.
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*
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* If CONFIG_ARCH_ROMGETC is defined, then the architecture logic must
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* export the function up_romgetc(). up_romgetc() will simply read one
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* byte of data from the instruction space.
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*
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* If CONFIG_ARCH_ROMGETC, certain C stdio functions are effected: (1)
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* All format strings in printf, fprintf, sprintf, etc. are assumed to
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* lie in FLASH (string arguments for %s are still assumed to reside in
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* SRAM). And (2), the string argument to puts and fputs is assumed to
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* reside in FLASH. Clearly, these assumptions may have to modified for
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* the particular needs of your environment. There is no "one-size-fits-all"
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* solution for this problem.
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*
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****************************************************************************/
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char up_romgetc(FAR const char *ptr)
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{
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/* This is basically a No-Op if enabled in the simulation environment */
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return *ptr;
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}
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#endif
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