won’t know what to do next! The section of memory just paged in
must, in this situation, contain the next program instruction
and it must be located at the next consecutive address to that
in the program counter at the time of changing page.
I have found this facility particularly useful whilst
developing programs destined to reside in ROM in my paged EPROM
board. Experience has shown that it is all too easy to make
mistakes in shifting control from one page to another, and
re-programming EPROMs is a tedious business! The paged RAM in the
provides an easy way of simulating the paged EPROM,
allowing easy testing and modification without the need to
re-program an EPROM every time.
Another possible use for the AVC memory is to hold large
blocks of data to which the main program (in normal RAM) refers
only when required. This could arise, for example, in database
programs, word-processor or financial applications ... in fact,
wherever memory capacity is being strained by storage of large
amounts of data, look up tables, etc.
I hope this article will stimulate other owners of the AVC
to suggest more ‘unadvertised’ uses for this excellent, but
poorly promoted, board.
Incidentally, reverting momentarily to the graphics
application of the AVC, I am having trouble patching into the
DUMP command due, I believe, to an error in the Lucas software
or manual. If anyone has dealt with this problem I would be
pleased to hear from them.
Machine code program to page-in the required 16K page of memory
and return contral to Nas-Sys.
xx=00 for normal system RAM
xx=01 for AVC ‘RED’ page
xx=02 for AVC ‘GREEN’ page
xx=03 for AVC ‘BLUE’ page