EBTKS Memory Map for the AUXROM(s)

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


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


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 How Mailboxes and Buffers Work While the rest of each AUXROM is unique, there is a situation where duplication of code is advantageous Fast inter-ROM jumps .

Detailed view of the AUXROM shared RAM area


AUXROM Shared RAM: Usage Plan

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