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Epiphany Specific Information
#############################
This chapter discusses the`Epiphany Architecture <http://adapteva.com/docs/epiphany_sdk_ref.pdf>`_
dependencies in this port of RTEMS. Epiphany is a chip that can come with 16 and
64 cores, each of which can run RTEMS separately or they can work together to
run a SMP RTEMS application.
**Architecture Documents**
For information on the Epiphany architecture refer to the`Epiphany Architecture Reference <http://adapteva.com/docs/epiphany_arch_ref.pdf>`_.
Calling Conventions
===================
Please refer to the`Epiphany SDK <http://adapteva.com/docs/epiphany_sdk_ref.pdf>`_
Appendix A: Application Binary Interface
Floating Point Unit
-------------------
A floating point unit is currently not supported.
Memory Model
============
A flat 32-bit memory model is supported, no caches. Each core has its own 32 KiB
strictly ordered local memory along with an access to a shared 32 MiB external
DRAM.
Interrupt Processing
====================
Every Epiphany core has 10 exception types:
- Reset
- Software Exception
- Data Page Fault
- Timer 0
- Timer 1
- Message Interrupt
- DMA0 Interrupt
- DMA1 Interrupt
- WANT Interrupt
- User Interrupt
Interrupt Levels
----------------
There are only two levels: interrupts enabled and interrupts disabled.
Interrupt Stack
---------------
The Epiphany RTEMS port uses a dedicated software interrupt stack.
The stack for interrupts is allocated during interrupt driver initialization.
When an interrupt is entered, the _ISR_Handler routine is responsible for
switching from the interrupted task stack to RTEMS software interrupt stack.
Default Fatal Error Processing
==============================
The default fatal error handler for this architecture performs the
following actions:
- disables operating system supported interrupts (IRQ),
- places the error code in ``r0``, and
- executes an infinite loop to simulate a halt processor instruction.
Symmetric Multiprocessing
=========================
SMP is not supported.
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.
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