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**********************************
EBTKS Memory Map for the AUXROM(s)
**********************************

**This is the standard memory layout for the HP-85 A and B**

.. image::  _images/Memory_Layout.png
   :height: 800px
   :align:  center
   :target: _images/Memory_Layout.png

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The AUXROM is implemented as one of the option ROMs on the right side
of the above diagram

**This is the detailed view of the AUXROM and its 13 additional extension ROMs**

.. image::  _images/AUXROM_Layout.png
   :height: 800px
   :align:  center
   :target: _images/AUXROM_Layout.png

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.. Note: display a short link name for a long heading

.. |shortlink01| replace:: How Mailboxes and Buffers Work
.. _shortlink01: :ref:`How Mailboxes, Buffers, Buffer Lengths, and Usage Codes Work`

When any of the AUXROMs are selected, a shared/common block of RAM is
available that can be both read and written by EBTKS and the software
in the AUXROMs. To manage **write access** to this shared area, a set
of 32 mailboxes are provided
:ref:`How Mailboxes and Buffers Work <How Mailboxes, Buffers, Buffer Lengths, and Usage Codes Work>`
While the rest of each
AUXROM is unique, there is a situation where duplication of code is
advantageous :ref:`Fast inter-ROM jumps` .

Detailed view of the AUXROM shared RAM area
-------------------------------------------

.. image::  _images/AUXROM_RAM_Layout.png
   :height: 800px
   :align:  center
   :target: _images/AUXROM_RAM_Layout.png

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AUXROM Shared RAM: Usage Plan
.............................

The details of how the shared RAM area is used is described in the
paragraphs, starting here :ref:`AUXROM Shared RAM: Buffers`