source: rtems-docs/cpu_supplement/superh.rst @ 489740f

.. comment SPDX-License-Identifier: CC-BY-SA-4.0

SuperH Specific Information
###########################

This chapter discusses the SuperH architecture dependencies
in this port of RTEMS.  The SuperH family has a wide variety
of implementations by a wide range of vendors.  Consequently,
there are many, many CPU models within it.

**Architecture Documents**

For information on the SuperH architecture,
refer to the following documents available from VENDOR
(:file:`http//www.XXX.com/`):

- *SuperH Family Reference, VENDOR, PART NUMBER*.

CPU Model Dependent Features
============================

This chapter presents the set of features which vary
across SuperH implementations and are of importance to RTEMS.
The set of CPU model feature macros are defined in the file``cpukit/score/cpu/sh/sh.h`` based upon the particular CPU
model specified on the compilation command line.

Another Optional Feature
------------------------

The macro XXX

Calling Conventions
===================

Calling Mechanism
-----------------

All RTEMS directives are invoked using a ``XXX``
instruction and return to the user application via the``XXX`` instruction.

Register Usage
--------------

The SH1 has 16 general registers (r0..r15).

- r0..r3 used as general volatile registers

- r4..r7 used to pass up to 4 arguments to functions, arguments
  above 4 are
  passed via the stack)

- r8..13 caller saved registers (i.e. push them to the stack if you
  need them inside of a function)

- r14 frame pointer

- r15 stack pointer

Parameter Passing
-----------------

XXX

Memory Model
============

Flat Memory Model
-----------------

The SuperH family supports a flat 32-bit address
space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4
gigabytes).  Each address is represented by a 32-bit value and
is byte addressable.  The address may be used to reference a
single byte, word (2-bytes), or long word (4 bytes).  Memory
accesses within this address space are performed in big endian
fashion by the processors in this family.

Some of the SuperH family members support virtual memory and
segmentation.  RTEMS does not support virtual memory or
segmentation on any of the SuperH family members.  It is the
responsibility of the BSP to initialize the mapping for
a flat memory model.

Interrupt Processing
====================

Although RTEMS hides many of the processor dependent
details of interrupt processing, it is important to understand
how the RTEMS interrupt manager is mapped onto the processor's
unique architecture. Discussed in this chapter are the MIPS's
interrupt response and control mechanisms as they pertain to
RTEMS.

Vectoring of an Interrupt Handler
---------------------------------

Upon receipt of an interrupt the XXX family
members with separate interrupt stacks automatically perform the
following actions:

- TBD

A nested interrupt is processed similarly by these
CPU models with the exception that only a single ISF is placed
on the interrupt stack and the current stack need not be
switched.

Interrupt Levels
----------------

TBD

Default Fatal Error Processing
==============================

The default fatal error handler for this architecture disables processor
interrupts, places the error code in *XXX*, and executes a ``XXX``
instruction to simulate a halt processor instruction.

Symmetric Multiprocessing
=========================

SMP is not supported.

Thread-Local Storage
====================

Thread-local storage is not implemented.

Board Support Packages
======================

System Reset
------------

An RTEMS based application is initiated or
re-initiated when the processor is reset.  When the
processor is reset, it performs the following actions:

- TBD

Processor Initialization
------------------------

TBD

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.. COMMENT: On-Line Applications Research Corporation (OAR).

.. COMMENT: All rights reserved.