Architecture-Specific Code
^^^^^^^^^^^^^^^^^^^^^^^^^^
Table of Contents
^^^^^^^^^^^^^^^^^

o Architecture-Specific Code
o Summary of Files
o Supported Architectures
o Configuring NuttX

Architecture-Specific Code
^^^^^^^^^^^^^^^^^^^^^^^^^^

The NuttX configuration consists of:

o Processor architecture specific files. These are the files contained
in the arch// directory discussed in this README.

o Chip/SoC specific files. Each processor processor architecture
is embedded in chip or System-on-a-Chip (SoC) architecture. The
full chip architecture includes the processor architecture plus
chip-specific interrupt logic, general purpose I/O (GIO) logic, and
specialized, internal peripherals (such as UARTs, USB, etc.).

These chip-specific files are contained within chip-specific
sub-directories in the arch// directory and are selected
via the CONFIG_ARCH_name selection

o Board specific files. In order to be usable, the chip must be
contained in a board environment. The board configuration defines
additional properties of the board including such things as
peripheral LEDs, external peripherals (such as network, USB, etc.).

These board-specific configuration files can be found in the
configs// sub-directories.

This README will address the processor architecture specific files
that are contained in the arch// directory. The file
include/nuttx/arch.h identifies all of the APIs that must
be provided by this architecture specific logic. (It also includes
arch//arch.h as described below).

Directory Structure
^^^^^^^^^^^^^^^^^^^

The arch/ directory contains architecture-specific logic. The complete
board port is defined by the architecture-specific code in this
directory plus the board-specific configurations in the config/
subdirectory. Each architecture must provide a subdirectory
under arch/ with the following characteristics:


/
|-- include/
| |--/
| | `-- (chip-specific header files)
| |--/
| |-- arch.h
| |-- irq.h
| `-- types.h
`-- src/
|--/
| `-- (chip-specific source files)
|--/
|-- Makefile
`-- (architecture-specific source files)

Summary of Files
^^^^^^^^^^^^^^^^

include//
This sub-directory contains chip-specific header files.

include/arch.h
This is a hook for any architecture specific definitions that may
be needed by the system. It is included by include/nuttx/arch.h

include/types.h
This provides architecture/toolchain-specific definitions for
standard types. This file should typedef:

_int8_t, _uint8_t, _int16_t, _uint16_t, _int32_t, _uint32_t

and if the architecture supports 64-bit integers:

_int24_t, _uint24_t, _int64_t, _uint64_t

NOTE that these type names have a leading underscore character. This
file will be included(indirectly) by include/stdint.h and typedef'ed to
the final name without the underscore character. This roundabout way of
doings things allows the stdint.h to be removed from the include/
directory in the event that the user prefers to use the definitions
provided by their toolchain header files.

irqstate_t

Must be defined to the be the size required to hold the interrupt
enable/disable state.

This file will be included by include/sys/types.h and be made
available to all files.

include/irq.h
This file needs to define some architecture-specific functions (usually
inline if the compiler supports inlining) and structures. These include:

- struct xcptcontext. This structure represents the saved context
of a thread.

- irqstate_t up_irq_save(void) -- Used to disable all interrupts.

- void upirq_restore(irqstate_t flags) -- Used to restore interrupt
enables to the same state as before up_irq_save was called.

NOTE: These interfaces are not available to application code but can
only be used within the operating system code. And, in general,
these functions should *never* be called directly, not unless you
know absolutely well what you are doing. Rather you shoudl typically
use the wrapper functions enter_critical_section() and leave_critical_section()
as prototyped in include/nuttx/irq.h.

This file must also define NR_IRQS, the total number of IRQs supported
by the board.

src//
This sub-directory contains chip-specific source files.

src/Makefile
This makefile will be executed to build the targets src/libup.a and
src/up_head.o. The up_head.o file holds the entry point into the system
(power-on reset entry point, for example). It will be used in
the final link with libup.a and other system archives to generate the
final executable.

Supported Architectures
^^^^^^^^^^^^^^^^^^^^^^^
NOTE: nuttx/Documentation/NuttX.html for current information about the
state of these MCU ports.

arch/sim - Linux/Cygwin simulation
A user-mode port of NuttX to the x86 Linux platform is available.
The purpose of this port is primarily to support OS feature development.
This port does not support interrupts or a real timer (and hence no
round robin scheduler) Otherwise, it is complete.

arch/arm - ARM-based micro-controllers
This directory holds common ARM architectures. At present, this includes
the following subdirectories:

Architecture Support
arch/arm/include and arch/arm/src/common
arch/arm/src/arm and arch/arm/include/arm
arch/arm/src/armv7-a and arch/arm/include/armv6-m
arch/arm/src/armv7-a and arch/arm/include/armv7-a
arch/arm/src/armv7-m and arch/arm/include/armv7-m
arch/arm/src/armv7-r and arch/arm/include/armv7-r

MCU support
arch/arm/include/a1x and arch/arm/src/a1x
arch/arm/include/am335x and arch/arm/src/am335x
arch/arm/include/c5471 and arch/arm/src/c5471
arch/arm/include/dm320 and arch/arm/src/dm320
arch/arm/include/efm32 and arch/arm/src/efm32
arch/arm/include/imx1 and arch/arm/src/imx1
arch/arm/include/imx6 and arch/arm/src/imx6
arch/arm/include/imx6 and arch/arm/src/imrt
arch/arm/include/kinetis and arch/arm/src/kinetis
arch/arm/include/kl and arch/arm/src/kl
arch/arm/include/lpc11xx and arch/arm/src/lc823450
arch/arm/include/lpc11xx and arch/arm/src/lpc11xx
arch/arm/include/lpc17xx and arch/arm/src/lpc17xx
arch/arm/include/lpc214x and arch/arm/src/lpc214x
arch/arm/include/lpc2378 and arch/arm/src/lpc2378.
arch/arm/include/lpc31xx and arch/arm/src/lpc31xx
arch/arm/include/lpc43xx and arch/arm/src/lpc43xx
arch/arm/include/lpc43xx and arch/arm/src/lpc54xx
arch/arm/include/lpc43xx and arch/arm/src/max236xx
arch/arm/include/moxart and arch/arm/src/moxart
arch/arm/include/nuc1xx and arch/arm/src/nrf52
arch/arm/include/nuc1xx and arch/arm/src/nuc1xx
arch/arm/include/sam34 and arch/arm/src/sam34
arch/arm/include/sama45 and arch/arm/src/sama5
arch/arm/include/samd2l2 and arch/arm/src/samd2l2
arch/arm/include/samd2l2 and arch/arm/src/samd5e5
arch/arm/include/samv7 and arch/arm/src/samv7
arch/arm/include/stm32 and arch/arm/src/stm32
arch/arm/include/stm32f7 and arch/arm/src/stm32f0
arch/arm/include/stm32f7 and arch/arm/src/stm32f7
arch/arm/include/stm32l4 and arch/arm/src/stm32h7
arch/arm/include/stm32l4 and arch/arm/src/stm32l4
arch/arm/include/str71x and arch/arm/src/str71x
arch/arm/include/tiva and arch/arm/src/tiva
arch/arm/include/tms570 and arch/arm/src/tms570
arch/arm/include/tms570 and arch/arm/src/xmc4

arch/avr
This directory is dedicated to ports to the Atmel AVR (8-bit) and AVR32 (32-bit)
MCU families. STATUS: Under development.

Architecture Support
arch/avr/include/avr and arch/avr/src/avr
arch/avr/include/avr32 and arch/avr/src/avr32

MCU support
arch/avr/include/atmega and arch/avr/src/atmega
arch/avr/include/at90usb and arch/avr/src/at90usb
arch/avr/include/at32uc3 and arch/avr/src/at32uc3

arch/hc
This directory is dedicated to ports to the Freescale HC family.

arch/arm/include/m9s12 and arch/arm/src/m9s12

arch/mips
This directory is dedicated to ports to the MIPS family.

Architecture Support
arch/mips/include/mips32 and arch/mips/src/mips32

MCU support
arch/mips/include/pic32mx and arch/mips/src/pic32mx
arch/mips/include/pic32mz and arch/mips/src/pic32mz

arch/renesas - Support for Renesas and legacy Hitachi microcontrollers.
This include SuperH and M16C.

Architecture Support
arch/renesas/include and arch/renesas/src/common

MCU support
arch/renesas/include/m16c and arch/renesas/src/m16c
arch/renesas/include/sh1 and arch/renesas/src/sh1

arch/or1k
This directory is dedicated to ports to OpenRISC architectures.

arch/or1k/include/mor1k and arch/or1k/src/mor1k

arch/risc-v
This directory is dedicated to ports to the RISC-V family.

Architecture Support
arch/risc-v/include/rv32im

MCU support
arch/risc-v/include/gap8
arch/risc-v/include/nr5m100

arch/x86 - Intel x86 architectures
This directory holds related, 32- and 64-bit architectures from Intel.
At present, this includes the following subdirectories:

Architecture Support
arch/x86/include and arch/x86/src/common

MCU support
arch/x86/include/i486 and arch/x86/src/i486
arch/x86/include/qemu and arch/x86/src/qemu

arch/xtensa

Implementations based on the Cadence® Tensilica® Xtensa® processors,
such as the Xtensa LX6 dataplane processing units (DPUs). At
present, this includes the following subdirectories:

Common XTENSA support:
arch/xtensa/include and arch/xtensa/src/common

LX6 DPU support:
arch/xtensa/include/lx6 and arch/xtensa/xtensa/lx6

Expressif ESP32 implemenation of the LX6 DPU:
arch/xtensa/include/esp32 and arch/xtensa/xtensa/esp32

arch/z16 - ZiLOG 16-bit processors
This directory holds related, 16-bit architectures from ZiLOG. At
present, this includes the following subdirectories:

Architecture Support
arch/z16/include and arch/z16/src/common

MCU support
arch/z16/include/z16f and arch/z16/src/z16f

arch/z80 - ZiLOG 8-bit microcontrollers
This directory holds related, 8-bit architectures from ZiLOG. At
present, this includes the following subdirectories:

Architecture Support
arch/z80/include and arch/z80/src/common

MCU support
arch/z80/include/ez80 and arch/z80/src/ez80
arch/z80/include/z80 and arch/z80/src/z180
arch/z80/include/z8 and arch/z80/src/z8
arch/z80/include/z80 and arch/z80/src/z80