72 lines
3.3 KiB
Plaintext
72 lines
3.3 KiB
Plaintext
|
/*
|
||
|
|
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
|
||
|
|
|
||
|
|
This file is part of ChibiOS/RT.
|
||
|
|
|
||
|
|
ChibiOS/RT is free software; you can redistribute it and/or modify
|
||
|
|
it under the terms of the GNU General Public License as published by
|
||
|
|
the Free Software Foundation; either version 3 of the License, or
|
||
|
|
(at your option) any later version.
|
||
|
|
|
||
|
|
ChibiOS/RT is distributed in the hope that it will be useful,
|
||
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
|
|
GNU General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU General Public License
|
||
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @defgroup PAL PAL Driver
|
||
|
|
* @brief I/O Ports Abstraction Layer
|
||
|
|
* @details This module defines an abstract interface for digital I/O ports.
|
||
|
|
* Note that most I/O ports functions are just macros. The macros
|
||
|
|
* have default software implementations that can be redefined in a
|
||
|
|
* PAL Low Level Driver if the target hardware supports special features like,
|
||
|
|
* as example, atomic bit set/reset/masking. Please refer to the ports specific
|
||
|
|
* documentation for details.<br>
|
||
|
|
* The @ref PAL has the advantage to make the access to the I/O ports platform
|
||
|
|
* independent and still be optimized for the specific architectures.<br>
|
||
|
|
* Note that the PAL Low Level Driver may also offer non standard macro and
|
||
|
|
* functions in order to support specific features but, of course, the use of
|
||
|
|
* such interfaces would not be portable. Such interfaces shall be marked with
|
||
|
|
* the architecture name inside the function names.
|
||
|
|
* @pre In order to use the ADC driver the @p CH_HAL_USE_PAL option
|
||
|
|
* must be enabled in @p halconf.h.
|
||
|
|
*
|
||
|
|
* @section pal_1 Implementation Rules
|
||
|
|
* In implementing a PAL Low Level Driver there are some rules/behaviors that
|
||
|
|
* should be respected.
|
||
|
|
*
|
||
|
|
* @subsection pal_1_1 Writing on input pads
|
||
|
|
* The behavior is not specified but there are implementations better than
|
||
|
|
* others, this is the list of possible implementations, preferred options
|
||
|
|
* are on top:
|
||
|
|
* -# The written value is not actually output but latched, should the pads
|
||
|
|
* be reprogrammed as outputs the value would be in effect.
|
||
|
|
* -# The write operation is ignored.
|
||
|
|
* -# The write operation has side effects, as example disabling/enabling
|
||
|
|
* pull up/down resistors or changing the pad direction. This scenario is
|
||
|
|
* discouraged, please try to avoid this scenario.
|
||
|
|
* .
|
||
|
|
* @subsection pal_1_2 Reading from output pads
|
||
|
|
* The behavior is not specified but there are implementations better than
|
||
|
|
* others, this is the list of possible implementations, preferred options
|
||
|
|
* are on top:
|
||
|
|
* -# The actual pads states are read (not the output latch).
|
||
|
|
* -# The output latch value is read (regardless of the actual pads states).
|
||
|
|
* -# Unspecified, please try to avoid this scenario.
|
||
|
|
* .
|
||
|
|
* @subsection pal_1_3 Writing unused or unimplemented port bits
|
||
|
|
* The behavior is not specified.
|
||
|
|
*
|
||
|
|
* @subsection pal_1_4 Reading from unused or unimplemented port bits
|
||
|
|
* The behavior is not specified.
|
||
|
|
*
|
||
|
|
* @subsection pal_1_5 Reading or writing on pins associated to other functionalities
|
||
|
|
* The behavior is not specified.
|
||
|
|
*
|
||
|
|
* @ingroup IO
|
||
|
|
*/
|