102 lines
4.6 KiB
C
102 lines
4.6 KiB
C
/****************************************************************************
|
|
* arch/sim/src/up_romgetc.c
|
|
*
|
|
* Copyright (C) 2011 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
*
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. 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.
|
|
* 3. Neither the name NuttX nor the names of its 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 OWNER 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.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
|
|
#include <nuttx/arch.h>
|
|
|
|
#ifdef CONFIG_ARCH_ROMGETC
|
|
|
|
/****************************************************************************
|
|
* Private Definitions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Data
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: up_romgetc
|
|
*
|
|
* Description:
|
|
* In Harvard architectures, data accesses and instruction accesses occur
|
|
* on different busses, perhaps concurrently. All data accesses are
|
|
* performed on the data bus unless special machine instructions are
|
|
* used to read data from the instruction address space. Also, in the
|
|
* typical MCU, the available SRAM data memory is much smaller that the
|
|
* non-volatile FLASH instruction memory. So if the application requires
|
|
* many constant strings, the only practical solution may be to store
|
|
* those constant strings in FLASH memory where they can only be accessed
|
|
* using architecture-specific machine instructions.
|
|
*
|
|
* A similar case is where strings are retained in "external" memory such
|
|
* as EEPROM or serial FLASH. This case is similar only in that again
|
|
* special operations are required to obtain the string data; it cannot
|
|
* be accessed directly from a string pointer.
|
|
*
|
|
* If CONFIG_ARCH_ROMGETC is defined, then the architecture logic must
|
|
* export the function up_romgetc(). up_romgetc() will simply read one
|
|
* byte of data from the instruction space.
|
|
*
|
|
* If CONFIG_ARCH_ROMGETC, certain C stdio functions are effected: (1)
|
|
* All format strings in printf, fprintf, sprintf, etc. are assumed to
|
|
* lie in FLASH (string arguments for %s are still assumed to reside in
|
|
* SRAM). And (2), the string argument to puts and fputs is assumed to
|
|
* reside in FLASH. Clearly, these assumptions may have to modified for
|
|
* the particular needs of your environment. There is no "one-size-fits-all"
|
|
* solution for this problem.
|
|
*
|
|
****************************************************************************/
|
|
|
|
char up_romgetc(FAR const char *ptr)
|
|
{
|
|
/* This is basically a No-Op if enabled in the simulation environment */
|
|
|
|
return *ptr;
|
|
}
|
|
#endif
|